september 2, 2016 waldhotel national, arosa, switzerland ...nvlad/ecti_conference...1 timetable...

ECTI 20164th European Conference on Trapped Ions

August 29 - September 2, 2016Waldhotel National, Arosa, Switzerland

http://www.tiqi.ethz.ch/ecti-2016.html

We gratefully acknowledge support from our industrial sponsors:

as well as from our institutional partners:

Kontaktgruppe für Forschungsfragen (KGF):

Contents

Timetable 1

Talk abstracts 10

List of posters 96

Poster abstracts 97

List of participants 179

Committees 185

WIFI access and Conference hike 187

1

TimetableMonday, August 29

11:00–14:30 Registration

Session chair: Jonathan Home

14:30–14:45 Welcome + opening of the meeting

14:45–15:30 Opening lecture: David Wineland

(NIST, Boulder, US)

Paul trap quantum information processing at

NIST

15:30–16:00 Jeremy Sage (MIT Lincoln Lab., MA, US)

Integrated photonics for trapped-ion control

16:00–16:30 Chris Ballance (University of Oxford, UK)

Quantum Logic with Lasers and Microwaves

16:30–17:00 Coffee break

Session chair: Michael Drewsen

17:00–17:30 Olivier Dulieu (Laboratoire Aimé Cotton, CNRS,

FR) Cold ions and atoms in hybrid traps:

premises of cold chemistry

17:30–18:00 Sadiqali A. Rangwala (Raman Research Insti-

tute, Bangalore, IN)

The atom-cavity collective strong coupling

measurement of ion-atom collisions

18:00–18:30 Daniel Comparat (Laboratoire Aimé Cotton,

CNRS, FR)

Molecular anions and laser cooling (even for

neutral molecules !)

2

18:30–20:30 Dinner

20:30–22:30 Poster session 1 (odd-numbered posters)

Tuesday, August 30

08:00–09:00 Breakfast

Session chair: Markus Hennrich

09:00–09:30 Ferdinand Schmidt-Kaler

(University of Mainz, DE)

Rydberg excitation of trapped cold ions

09:30–10:00 Antoine Browaeys

(Laboratoire Charles Fabry, CNRS, FR)

Implementation of spin hamiltonians in ar-

rays of individual Rydberg atoms

10:00–10:30 Tilman Pfau (University of Stuttgart, DE)

Investigating self–bound droplets of a dilute

magnetic quantum liquid


Session chair: Tanja Mehlstäubler

11:00–11:30 Murray Barrett

(Center for Quantum Technologies, and National

University of Singapore, SG)

Progress towards a lutetium ion optical clock

11:30–12:00 Helen Margolis (NPL, Teddington, UK)

International frequency comparisons between

trapped ion optical clocks

3

12:00–12:30 Matt Grau (JILA, NIST and University of Col-

orado, US)

Measuring the electron EDM with trapped

molecular ions

12:30–14:30 Lunch

Session chair: Joe Britton

14:30–15:30 Sebastian George (Max-Planck-Institut für Kern-

physik, DE)

First Results from the Cryogenic Storage Ring

CSR

15:00–15:30 Martina Knoop (Aix-Marseille University, CNRS,

FR)

Number diagnostic of a long ion chain

15:30–16:00 Justin Bohnet (NIST, Boulder, US)

Signatures of entanglement in a quantum

simulator with hundreds of trapped ions

16:00–16:30 Richard Thompson

(Imperial College London, UK)

Professor Danny Segal: his contributions to

research with Penning traps and to the ion

trap communtity


4

Session chair: Alex Retzker

17:00–17:30 Christopher Monroe

(JQI and University of Maryland, US)

Fast Gates and Slow Spin Models

17:30–18:00 Christian F. Roos (IQOQI Innsbruck, AT)

Characterizing the non-equilibrium dynam-

ics of ion strings with up to twenty ions simu-

lating Ising interactions

18:00–18:30 Diego Porras

(University of Sussex, UK)

Trapped ion spin-boson quantum simulators

18:30–20:30 Dinner

20:30–22:30 Poster session 2 (even-numbered posters)

Wednesday, August 31


Session chair: Stefan Willitsch

09:00–09:30 Roland Wester (University of Innsbruck, AT)

Rotational state-to-state collisions of cold

molecular ions

09:30–10:00 Tim Softley (University of Birmingham, UK)

Cold chemical reactions using trapped and

sympathetically cooled ions

5

10:00–10:30 Alexander Dörfler (University of Basel, CH)

A dynamic ion-atom hybrid trap for high-

resolution cold-collision studies

T. Sikorsky (Weizmann Institute of Science, IL)

Dynamics of a ground-state cooled ion collid-

ing with ultra-cold atoms


Session chair: Dietrich Leibfried

11:00–11:30 Kihwan Kim (Tsinghua University, Beijing, CN)

Long coherence time of single quantum bit in

a two-species ion trap

11:30–12:00 Kenji Toyoda (Osaka University, JP)

Quantum information processing and quan-

tum simulation based on phonons in trapped

ions

12:00–12:30 Alex Retzker (Hebrew University of Jerusalem, IL)

Refocusing two qubit gates with measure-

ments for trapped ions

Vlad Negnevitsky (ETH Zürich, CH)

Quantum nondemolition parity measure-

ment and Bayesian-assisted techniques in a

mixed-species ion crystal

12:30–12:30 Lunch pack

13:00–16:30 Free afternoon or Conference hike

18:30–20:30 Dinner

6

Session chair: Winfried Hensinger

20:30–21:30 Evening lecture: Rainer Blatt

(University of Innsbruck, IQOQI Innsbruck, AT)

The Jaynes-Cummings Hamiltonian in

Trapped-Ion Physics

Thursday, September 1


Session chair: Laurent Hilico

09:00–09:30 Klaus Blaum (Max-Planck-Institut für Kern-

physik, DE)

Precision measurements of fundamental

properties of atomic particles in Penning traps

09:30–10:00 Stefan Ulmer (RIKEN, JP)

High-Precision Comparisons of the Funda-

mental Properties of the Proton and the An-

tiproton

10:00–10:30 Marianna S. Safronova

(University of Delaware, and JQI, NIST, and Uni-

versity of Maryland, US)

Search for new physics with highly charged

ions


7

Session chair: Caroline Champenois

11:00–11:30 Henrik Cederquist (Stockholm University, SE)

Experiments with stored ion beams at the DE-

SIREE facility in Stockholm

11:30–12:00 Christiane Koch (University of Kassel, DE)

The role of internal rotation in atom-molecule

collisions: Sympathetic cooling and cold reac-

tions

12:00–12:30 Mikhail Lemeshko (Institute of Science and

Technology Austria, AT)

Rotation of cold molecular ions inside a Bose-

Einstein condensate

12:30–14:30 Lunch

Session chair: Otto Dopfer

14:30–15:30 Thomas R. Rizzo (EPFL, CH)

Spectroscopy of Trapped, Mobility-Selected,

Biomolecular Ions

15:00–15:30 Stephan Schlemmer (University of Köln, DE)

Molecular Rotation of very floppy molecules,

the case of CH+515:30–16:00 Knut Asmis (University of Leipzig, DE)

Ion Microsolvation Probed by Cryogenic Ion

Trap Vibrational Spectroscopy

16:00–16:30 Chiara Masellis (EPFL, CH)

Using trapped ions, cryogenic spectroscopy,

and ion mobility to sequence carbohydrates

Markus Hennrich (Stockholm University, SE)

Observation of trap effects, EIT, and STIRAP

with a single Rydberg ion

8


Session chair: Christian Ospelkaus

17:00–17:30 Piet O. Schmidt

(PTB, and Leibniz Universität Hannover, DE)

Quantum logic with molecular ions

17:30–18:00 Chin-wen Chou (NIST, Boulder, US)

Preparation and coherent manipulation of

pure quantum states of a single molecular ion

Nils Huntemann (PTB, DE)

Search for violations of the equivalence prin-

ciple with 171Yb+ single-ion clocks and a 87Sr

lattice clock

18:00–18:30 Norbert Linke (JQI, UMD and NIST, US)

Quantum Algorithms on a Programmable

Quantum Computer

Philipp Schindler (University of Innsbruck, AT)

Simulating real-time dynamics of lattice

gauge theories with a few ions

19:00–19:30 Aperitif

19:30–20:30 Conference banquet

9

Friday, September 2


Session chair: Tracy Northup

09:00–09:30 Alexei Bylinskii (MIT, and currently at Harvard

University, US)

Friction under microscope in a trapped-ion

optical-lattice emulator

09:30–10:00 Aurelien Dantan (University of Aarhus, DK)

Spectroscopy of a single ion in a periodic opti-

cal potential

10:00–10:30 Tobias Schätz (University of Freiburg, DE)

Trapping ions optically


Session chair: David Lucas

11:00–11:30 Matthias Keller

(University of Sussex, UK)

Interfacing single ions and single photons

11:30–12:00 Christof Wunderlich (University of Siegen, DE)

Elements of quantum information science us-

ing radio-frequency driven trapped ions

12:00–12:30 Jürgen Eschner (University of Saarland, DE)

Interfacing a single ion with the telecom

wavelength range

Hendrik M. Meyer (University of Bonn, DE)

A single-ion coupled to a UV fiber-cavity

12:30–13:00 Close of the meeting

13:00–14:30 Lunch

10

Talk abstracts

11

Opening lecture

Paul trap quantum information processingat NIST

D. Allcock1, S. Burd1, S. Erickson1, D. Kienzler1, D. Leibfried1,

K. McCormick1, D. Slichter1, R. Srinivas1, T. R. Tan1, S. Todaro1,

Y. Wan1, A. Wilson1, D. Wineland1

1 National Institute of Standards and Technology, Boulder,

Colorado, 80305

David Wineland

[email protected]

We develop experimental methods to demonstrate the basic el-ements of quantum information processing using ions confinedin RF-Paul traps. Recent work includes high-fidelity laser-beam-induced gates [1], multi-species gates [2], Bell state preparationthrough Hilbert space engineering [3], and progress towardsimproved microwave-field-induced gates (D. Allcock, poster).Techniques include development of optically-pumped semi-conductor laser sources and UV-damage resistant optical fibers.Collaborative work to reduce ion heating is presented by D. Hiteat this conference. Molecular-ion spectroscopy experiments aredescribed by J. Chou. Related experiments using Penning trapsare described by J. Bohnet.

[1] J. Gaebler et al., arXiv:1604.00032.

[2] T. R. Tan et al., Nature 528, 380 (2015).

[3] Y. Lin et al., arXiv:1603.03848.

12

Invited talk

Integrated photonics for trapped-ion control

S. Bramhavar1, C.D. Bruzewicz1, D. Kharas1, R. McConnell1,

K.K. Mehta2, J. Plant1, C. Sorace-Agaskar1, R.J. Ram2, J. Chiaverini1,

J.M. Sage1

1MIT Lincoln Laboratory, Lexington, MA, USA.2Massachusetts Institute of Technology, Cambridge, MA, USA.

Jeremy Sage

[email protected]

A large system of individually-controllable trapped-ions could

enable large-scale quantum computing and reduce statistical

uncertainty in ion-based quantum sensors, such as atomic clocks.

A main obstacle to achieving the necessary control is the lack of a

means for delivering the required laser light to each ion in a large

array with sufficiently high intensity and low crosstalk. Integra-

tion of photonic structures into the ion trap, which are capable

of routing, splitting, and modulating light, presents a promis-

ing path towards the realization of individual control of a large

array of ions. In this talk, I will discuss our recent work demon-

strating coherent control of a trapped-ion qubit using silicon

nitride (SiN) photonics integrated into a surface-electrode ion

trap chip. In this proof-of-principle implementation, we show

on-chip light guiding and splitting and low crosstalk coupling

from the chip to the ion in free space [1].

Additionally, I will discuss our current efforts to develop ascalable SiN integrated photonics platform capable of deliveringmultiple wavelengths of visible light to ions, as well as a galliumnitride (GaN) platform for integrated visible-light electro-optic

13

modulators. The realization of these platforms would enablestate-preparation, control, and measurement of large arrays ofmultiple species of ions.

[1] K.K.. Mehta et al., arXiv:1510.05618.

14

Invited talk

Quantum Logic with Lasers and Microwaves

C. J. Ballance1

1Department of Physics, University of Oxford, Clarendon

Laboratory, Parks Road, Oxford, U.K.

Chris Ballance

[email protected]

Mixed-species quantum logic is a powerful technique for the

construction of a quantum computer based on trapped ions,

as it allows protection of memory qubits while other qubits un-

dergo logic operations, or are used as photonic interfaces to

other processing units. In our experiments, we generate a spin-

dependent force using a pair of laser beams that we have used to

entangle a 40Ca+ and a 43Ca+ ground-state qubit [1]. This same

gate mechanism can also be applied to entangle Ca+ and Sr+

qubits, and I will discuss our progress towards implementing

this.

I will also discuss our recent work on near-field microwave-driven two-qubit gates [2]. Using microwaves instead of lasersto drive two-qubit gates allows one to avoid certain sources oferror, for example photon scattering, and to take advantage ofthe maturity of microwave technology. However the long wave-length of microwave radiation leads to an inherently weak spin-motion coupling, making it challenging to achieve high-fidelitygates. We use a room-temperature surface trap with integratedmicrowave electrodes to implement a dynamically-decoupledvariant of a Mølmer-Sørensen gate. The gate is applied directly to43Ca+ ground-state ‘atomic clock’ qubits (coherence time T2 ≈ 50

15

sec), and we measure a Bell state fidelity of 99.7(1)%, represent-ing an improvement of approximately two orders of magnitudecompared with previous work [3].

[1] C. Ballance et al., Nature 528, 384 (2015)

[2] T. Harty et al., arXiv:1606.08409

[3] C. Ospelkaus et al., Nature 476, 181 (2011)

16

Invited talk

Cold ions and atoms in hybrid traps: premises ofcold chemistry

H. Da Silva Jr1, M. Raoult1, O. Dulieu1

1Laboratoire Aimé Cotton, CNRS, Université Paris-Sud, ENS

Cachan, Université Paris-Saclay, 91405 Orsay, France.

Olivier Dulieu

[email protected]

When traps of laser-cooled atomic ions A+ and trapped clouds

of ultracold atoms B are merged at the same spatial location,

a complex dynamics can take place, which prefigures the still

rising field of ultracold chemistry, dominated by the quantum

nature of the colliding particles involving resonances, tunnel-

ing ... Elastic, inelastic, reactive processes, possibly assisted by

the used laser light are all present in the experiment. Disentan-

gling all these processes is crucial for the demonstration and

the control of cold quantum chemistry. In this talk we will re-

port on the theoretical analysis of the formation and destruction

of cold molecular ions in such hybrid traps. Various mecha-

nisms for the formation of AB+ diatomic molecular ions will be

discussed (radiative association [1], three-body association [2])

which may compete with radiative and non-radiative charge

exchange processes. Furthermore, such ions are sensitive to

the remaining surrounding cold atoms through inelastic and

reactive collisions, and to the laser light used for cooling and

trapping through photodissociation [2].

This work is performed in close collaboration with the groupof J. Hecker Denschlag (Ulm Universität, Germany) and S. Rang-

17

wala (RRI, Bangalore, India).

[1] H. da Silva Jr, M. Raoult, M. Aymar, and O. Dulieu, J. Phys. B 17

045515, (2015).

[2] A. Krükow, A. Mohammadi, A. Härter, and J. Hecker Denschlag,

arxiv:1602.01381.

[3] S. Jyothi, T. Ray, S. Dutta, A. R. Allouche, R. Vexiau, O. Dulieu, S. A.

Rangwala, arxiv:1601.01119.

18

Invited talk

The atom-cavity collective strong couplingmeasurement of ion-atom collisions

Sourav Dutta1, S. A. Rangwala1

1Raman Research Institute, C. V. Raman Avenue, Sadashivanagar,

Bangalore 560080, India

Sadiq Rangwala

[email protected]

The study of interactions in dilute gas systems has resulted in

the creation of multiple designs of hybrid traps, where various

combinations of ions, atoms, molecules and light are confined

for specific measurements. The measurement of the interactions

between the trapped ensembles is very challenging, particularly

if each species has a different mechanism for detection. In such

a scenario, a generic tool for the detection of interactions is valu-

able. The collective strong coupling of atoms to the cavity in our

experiments [1, 2] can be utilized as a detector of interactions in

cold, dilute gas mixtures.Briefly, Rb atoms are created in a dark-MOT and Rb+ atoms

are cotrapped with the dark-MOT Rb atoms, within the modevolume of an optical Fabry-Pérot cavity. In this proof of principleexperiment, the signature of the atom-cavity collective strongcoupling, the vacuum Rabi splitting (VRS) changes, when theions are cotrapped with the dark-MOT atoms. The VRS mea-surement is performed on an open transition of the initiallyoptically dark Rb atom. The measurement itself is a frequencymeasurement, is fast, non-destructive, state selective and hassufficient fidelity to measure the ion-atom collision rate. Thetechnique is potentially universal as it uses the change in the

19

atom-cavity coupling to measure the effect of the undeterminedinteraction on the atom, thus affecting in a measurable waythe atom-cavity coupled oscillator system. Other realizations ofthis demonstration hold out the promise for a range of in-situinteraction measurements.

[1] T. Ray et al., Phys. Rev. A 87, 033832 (2013).

[2] S. Jyothi et al., in Ion Traps for Tomorrow’s Applications 269 – 278

(2015).

20

Invited talk

Molecular anions and laser cooling (even forneutral molecules !)

A. Cournol1, P. Yzombard1, P. Pillet1, H. Lignier1, D. Comparat1,

M. Doser2, S. Gerber2

1Laboratoire Aimé Cotton, CNRS, Univ. Paris-Sud, ENS Cachan,

Université Paris-Saclay, Bât. 505, 91405 Orsay, France.2CERN, European Laboratory for Particle Physics, 1211 Geneva,

Switzerland.

Daniel Comparat

[email protected]

Cooling and trapping molecules at ultracold temperatures wouldgive access to new quantum chemistry, studies of collective ef-fects, metrology of fundamental constants, etc. Direct cooling ofmolecules, based on supersonic expansion, cryogenic, or veloc-ity filtering, suffer from the fact that they pro- duce cold sampleof molecules moving at velocities of some hundred meters persecond. To stop molecules in the laboratory frame many experi-ments use electromagnetic decelerators acting on the electric ormagnetic permanent molecular dipole moment. However theseexisting methods have many drawbacks, such as high losses,cumbersome apparatus, ... We suggest a new approach con-sisting in electrically charging cooled neutral molecules, de-celerating the resulting anions over short distances, and finallyremoving the extra electron by photo-detachment [1, 2]. If sucha demonstration is successful, it will open the way to produceany (even if very heavy) polar molecules at rest. At middle termperspective, we consider some applications such as creation ofcold ion sources. We shall also present another alternative wayto get cold molecular anions by using standard laser cooling

21

techniques [4]. Combined with sympathetic cooling this schemeshould have an impact on charged particle sources, and anti-matter physics. We shall briefly explain why C−2 molecules aresuitable for such laser cooling schemes. If trapped this moleculecould potentially be cooled down to below 1 mK in only a fewtens of milliseconds, using standard lasers. We shall show thata scheme using more than one frequency per transition anddifferent polarization is required to create a significant force onthis J ← J −1 transition [3].

[1] M. Hamamda, P. Pillet, H. Lignier, D. Comparat, J. Phys. B: 48 182001

(2015).

[2] M. Hamamda, P. Pillet, H. Lignier D. Comparat, New J. Phys. 17,

045018 (2015).

[3] A. Cournol, P. Pillet, H. Lignier, D. Comparat, Phys. rev. A 93, 053423

(2016).

[4] P. Yzombard, M. Hamamda, S. Gerber, M. Doser, D. Comparat, Phys.

Rev. Lett. 114, 213001 (2015).

22

Invited talk

Rydberg excitation of trapped cold ions

T. Feldker, P. Bachor, J. Walz, F. Schmidt-Kaler1

1QUANTUM, Institut für Physik, Johannes Gutenberg-Universität

Mainz, Germany

Ferdinand Schmidt-Kaler

[email protected]

Atoms in highly excited Rydberg states have long radiative life-times and can have huge dipole moments. These unique proper-ties have enabled experiments in cavity quantum-electrodynamicsfor studying fundamental quantum physics [1], and also stronglong-range dipole-dipole interactions for quantum informationprocessing with neutral atoms [2]. Our experimental approachjoins the advantages of ion crystals for quantum informationprocessing with Rydberg states [2]. We demonstrate laser excita-tion of single trapped cold ions in a crystal e.g. on the 3d2D3/2to 52 and 53F, or the 3d2D5/2 to 66F and 22F transitions at wave-lengths near 122 nm, the observed lineshapes are well under-stood [4,5]. In combination with ion shuttling in the trap [6], weimplement addressed excitation and coherent initialization [5].This prepares the ground for using trapped Rydberg ions as anovel platform to realize quantum-gates or -simulations, andimplementing solid state models of quantum magnetism [7].In the outlook I describe how the interplay between long rangeCoulomb- and Rydberg-interactions allows for fast multi-qubitgate operations, the observation of novel many-body phenom-ena, and non-equilibrium dynamics.

[1] Brune, Schmidt-Kaler, Maali, Dreyer, Hagley, Raimond, Haroche,

PRL 76, 1800 (1996), Raimond, Brune, Haroche, RMP 73, 565 (2001).

[2] Saffman, Walker, Mølmer, RMP 82, 2313 (2010).

23

[3] Müller, Liang, Lesanovsky, Zoller, NJP 10, 093009 (2008), Schmidt-

Kaler, Feldker, Kolbe, Walz, Müller, P. Zoller, Li, Lesanovsky, NJP 13,

075014 (2011).

[4] Feldker, Bachor, Stappel, Kolbe, Gerritsma, Walz, Schmidt-Kaler,

PRL 115, 173001 (2015).

[5] Bachor, Feldker, Walz, Schmidt-Kaler, arXiv:1602.05006

[6] Walther et al., PRL 109, 080501 (2012), Ruster, et al., PRA 90, 033410

(2014).

[7] Nath, Dalmonte, Glaetzle, Zoller, Schmidt-Kaler, Gerritsma, NJP 17,

065018 (2015).

24

Invited talk

Implementation of spin hamiltonians in arraysof individual Rydberg atoms

D. Barredo1, S. Déléseleuc1, H. Labuhn1, S. Ravets1, V. Lienard1, T.

Macrì2, T. Lahaye1, A. Browaeys1

1Laboratoire Charles Fabry, Institut d’Optique, CNRS, Univ Paris

Sud, 2 Avenue Augustin Fresnel, 91127 Palaiseau cedex, France.2Departamento de Física Teoŕica e Experimental, Universidade

Federal do Rio Grande do Norte, and International Institute of

Physics, Natal-RN, Brazil.

Antoine Browaeys

[email protected]

This talk will present our on-going effort to control the dipole-

dipole interaction between cold Rydberg atoms in order to im-

plement spin Hamiltonians that may be useful for quantum

simulation of condensed matter problems. In our experiment,

we trap individual atoms in two-dimensional arrays of optical

tweezers [1] separated by few micrometers and excite them to

Rydberg states using lasers. The arrays are produced by a spa-

tial light modulator, which shapes the dipole trap beam. We

can create almost arbitrary, two- dimensional geometries of the

arrays.The talk will present our demonstration of the coherent en-

ergy exchange in small chains of Rydberg atoms resulting fromtheir dipole-dipole interaction [2]. This exchange interactionrealizes the XY spin model. We have also implemented the quan-tum Ising model [3]. The spin Hamiltonian is mapped onto asystem of Rydberg atoms excited by lasers and interacting by thevan der Waals Rydberg interaction. We study various configu-

25

rations such as one-dimensional chains of atoms with periodicboundary conditions, rings, or two-dimensional arrays contain-ing up to 30 atoms. We measure the dynamics of the excitationfor various strengths of the interactions between atoms. Wecompare the data with numerical simulations of this many-bodysystem and found excellent agreement for some of the configu-rations. This good control of an ensemble of interacting Rydbergatoms thus demonstrates a new promising platform for quan-tum simulation using neutral atoms, which is complementaryto the other platforms based on ions, magnetic atoms or dipolarmolecules.

[1] Nogrette et al., Phys. Rev. X 4, 021034 (2014).

[2] Barredo et al., Phys. Rev. Lett. 114, 113002 (2015).

[3] Labuhn et al., arXiv:1509.04543

26

Invited talk

Investigating self–bound droplets of a dilutemagnetic quantum liquid

T. Pfau1

15. Physikalisches Institut and Center for Integrated Quantum

Science and Technology, Universität Stuttgart.

Tilman Pfau

[email protected]

When studying the Rosensweig instability of a dipolar quan-

tum gas we found surprisingly long lifetimes of the droplets that

formed [1]. We have then identified the stabilization mecha-

nism based on beyond mean field term of the Lee-Huang-Yang

type, which arises due to quantum depletion of the factorizable

many–body groundstate. [2]. Based on this insight the corre-

sponding new state of matter has the characteristics of a liquid

including three dimensional self–bound droplet states which

we observe in a trap free levitation field. We find that magnetic

quantum droplets require a minimum critical number of atoms

below which they evaporate from a liquid droplet to an expand-

ing gas. The origin of this evaporation is the quantum pressure

of the individual constituents. Further studies on these droplets

include interference experiments and a study of their collective

oscillations.

Our work is based on ultracold bosonic Dysprosium atomswhich have a strong long range magnetic dipolar interactionand a tuneable repulsive short range contact interaction. Theinterplay of these two can be tuned such that the overall mean-field is weakly attractive but the mutual short range interaction

27

creates a quantum depletion and a corresponding many bodyrepulsion that counteracts the attraction at a stable density.

[1] H. Kadau, M. Schmitt, M. Wenzel, C. Wink, T. Maier, I. Ferrier-

Barbut, T. Pfau "Observing the Rosensweig instability of a quantum

ferrofluid", Nature 530, 194 (2016)

[2] I. Ferrier-Barbut, H. Kadau, M. Schmitt, M. Wenzel, T. Pfau, "Obser-

vation of quantum droplets in a strongly dipolar Bose gas", Physical

Review Letters 116, 215301 (2016)

28

Invited talk

Progress towards a lutetium ion optical clock

Kyle J. Arnold1, Rattakorn Kaewuam1,2, Eduardo Paez1,2, Samuel

Wang1,2, Arpan Roy1, and M. D. Barrett1,2.1Center for Quantum Technologies, 3 Science Drive 2, Singapore,

117543.2Department of Physics, National University of Singapore, 2 Science

Drive 3, Singapore, 117551.

Murray Barrett

[email protected]

We are investigating singly ionized lutetium as a potential op-tical clock candidate. By averaging over highly forbidden M1transitions to multiple hyperfine levels, we can realize an ef-fective frequency reference that is inherently insensitive to per-turbations arising from external electromagnetic fields [1]. Inaddition, lutetium offers intriguing possibilities for clock op-eration on a large Coulomb crystals which would significantlyimprove the stability of ion based clocks [2, 3]. We discuss theseideas and report our progress towards establishing a lutetiumion optical clock.

[1] M. D. Barrett, New Jour. Phys. 17, 053024 (2015).

[2] K. J. Arnold, et al., Phys. Rev. A. 92, 032108 (2015).

[3] K. J. Arnold and M. D. Barrett, arXiv:1607.04344 (2016).

29

Invited talk

International frequency comparisons betweentrapped ion optical clocks

H. S. Margolis1

1National Physical Laboratory (NPL), Teddington, Middlesex TW11

0LW, UK.

Helen Margolis

[email protected]

Optical atomic clocks based on single trapped ions have made

rapid progress over the past few years. The most advanced of

these clocks have now reached levels of stability and uncertainty

that significantly surpass the performance of caesium primary

standards. As a result of this and similar progress on neutral

atom optical lattice clocks, the possibility of a redefinition of the

SI second in terms of an optical transition frequency is being

considered by the international metrology community.

To validate the uncertainty budgets of the new generation of

optical clocks it is essential to compare the frequencies of clocks

developed by independent research groups in different labo-

ratories at a level commensurate with their performance. Until

recently, almost all such information about the reproducibility

of optical clocks came from independent absolute frequency

measurements made in different institutes, and was therefore

limited by the uncertainty of the local caesium primary stan-

dards used to realise the SI second.

This situation is now changing, with a variety of techniqueshaving recently been used to compare optical clocks directly. Inthis talk I will focus on the 171Yb+ trapped ion optical clocks de-

30

veloped at NPL and PTB, which we have now compared not onlyby means of independent absolute frequency measurements[1,2, 3], but also via GPS satellite links [4] and using a broadbandtwo-way time and frequency transfer technique. Further infor-mation about the clock reproducibility has been obtained bycomparing optical frequency ratio measurements [2] performedlocally within each laboratory. Comparisons via an optical fi-bre link will also be possible in the near future and will reducethe uncertainty of the clock comparisons below what can beachieved using satellite links.

[1] C. Tamm et al., Phys. Rev. A 89, 023820 (2014)

[2] R. M. Godun et al., Phys. Rev. Lett. 113, 210801 (2014)

[3] N. Huntemann et al., Phys. Rev. Lett. 113, 210802 (2014)

[4] J. Leute et al., IEEE Trans. UFFC 63, 981 (2016)

31

Invited talk

Measuring the electron EDM with trappedmolecular ions

M. Grau, W. Cairncross, D. N. Gresh, K. B. Ng, Y. Zhou, J. Ye, E. A.

Cornell

JILA, NIST and University of Colorado, and Department of Physics,

University of Colorado, USA.

Matt Grau

[email protected]

An electron electric dipole moment (eEDM) directly violatestime-reversal symmetry, which has implications for physics be-yond the Standard Model. An experiment using trapped molecu-lar ions offers high sensitivity because of the large effective elec-tric fields and long coherence times that are possible. Here wedemonstrate precision spectroscopy on many trapped HfF+ ionsin a radiofrequency quadrupole trap with rotating frame biasfields. We perform Ramsey spectroscopy between spin statesof the metastable 3∆1 level with a coherence time exceeding1 second. In contrast to preceding eEDM experiments usingmolecular beams, trapped ion experiments are sensitive to adifferent class of systematic effects. We will discuss systematicerrors arising from trapping and polarizing electric fields, mag-netic field gradients, and motional effects such as geometricphases preliminary eEDM measurement with a statistical sensi-tivity of 2×10−28 e-cm in 125 hours.

32

Invited talk

First Results from the Cryogenic Storage RingCSR

S. George1 for the CSR team1Max-Planck-Institut für Kernphysik, 69117, Heidelberg,

Deutschland.

Sebastian George

[email protected]

The Cryogenic Storage Ring (CSR) [1] located at the Max-Planck-

Institut für Kernphysik in Heidelberg, Germany, has been re-

cently commissioned. The CSR is an electrostatic storage ring

with 35 m circumference, which can be operated at tempera-

tures ranging from room temperature down to 1.8 K. Ion beams

with energies between 20 keV and 300 keV per charge unit are

injected from a high-voltage platform capable of housing a wide

variety of ion sources. A rich and manifold experimental pro-

gram aims at investigating ground state properties and colli-

sions of molecular and cluster ions in the gas phase. Due to

the cryogenic temperatures, extreme vacuum conditions with a

rest-gas density lower than 100 particles per cm3 (correspond-

ing to less than 10−14 mbar pressure at 300 K) can be reached,

which ensures storage times of more than 2500 s (1/e) for fast

ion beams. In addition, the low ambient temperatures of a few

Kelvin offer ion beam storage under conditions where warming

by blackbody radiation can be almost neglected in comparison

to standard laboratory experiments.

Pilot experiments demonstrated the experimental capabili-

ties of CSR. The photodissociation of an internally cold beam of

33

CH+ [2] stored for several minutes in an ambient temperature of

below 10 K in the CSR was studied. This allowed the observation

of Feshbach-type near-threshold photodissociation resonances

in the lowest rotational states J = 0−2.The storage-time dependent effective internal temperatures

of stored ions has been measured by internal state thermometry,

previously employed to determine the equilibrium rotational

temperature in a buffer-gas cooled radiofrequency trap [3]. Here,

near-threshold photodetachment spectroscopy of the hydroxyl

anion is used to observe the radiative cooling process until equi-

libration with the cryogenic ring environment. The rotational

level population was tracked for up to 20 minutes of storage

enabling a detailed analysis of the equilibrium conditions.

Furthermore, metal dimer anions have been used to demon-

strate the extremely long storage times and the sensitivity to

follow decay processes over several orders of magnitude.The status of CSR, first experimental results, and recent up-

grades will be presented in this talk.

[1] R. von Hahn et al., Rev. Sci. Instrum. 87, 063115 (2016).

[2] A.P. O’Connor et al., Phys. Rev. Lett. 116, 113002 (2016).

[3] R. Otto et al., Phys. Chem. Chem. Phys. 15, 612 (2013).

34

Invited talk

Number diagnostic of a long ion chain

M.R. Kamsap1, C. Champenois1, J. Pedregosa-Gutierrez1, M.

Houssin1, M. Knoop1

1Aix-Marseille Université, CNRS, PIIM, UMR 7345, 13397 Marseille,

France.

Martina Knoop

[email protected]

Very long, one-dimensional (1D) ion chains are the basis formany applications, in particular in quantum information pro-cessing [1]. In our double trap set-up we can create chains ofmore than 150 atoms, and count individual ions by translatingthe detection optics with micrometer resolution. We have exper-imentally validated Dubin’s law for very long ion chains [2] withhigh significance. This diagnostic allows to precisely determinethe number of trapped ions in long chains by measuring theion-ion distance of only the innermost particles, as well as thetrapping potential along the ion chain. In our experiment, thecentral 30 ions are measured to be equidistant to better than 2%,and we can determine the total number of trapped ions witha 4.5% uncertainty, completely dominated by a conservativeestimation of the experimental characterisation of the trap.[3].

[1] G.-D. Lin, et al., EPL 86, 60004 (2009)

[2] D.H.E. Dubin, Phys. Rev. Lett. 71, 2753 (1993); Phys. Rev. E 55, 4017

(1997).

[3] M.R. Kamsap, et al., arXiv:1604.04303.

35

Invited talk

Signatures of entanglement in a quantumsimulator with hundreds of trapped ions

J. G. Bohnet1, B. C. Sawyer2, J. W. Britton3, M. L. Wall4, A.

Safavinaini4, M. Foss-Feig3, M. Gaerttner4, A. M. Rey5, J. J. Bollinger1

1National Institute of Standards and Technology (NIST) Boulder,

Boulder, Colorado 80305, USA.2Georgia Tech Research Institute, Atlanta, Georgia 30332, USA.

3Army Research Lab, Adelphi, MD 20783, USA.4JILA, NIST and University of Colorado, Boulder, Colorado, 80309,

USA.5JILA, NIST and Department of Physics, University of Colorado,

Boulder, Colorado 80309, USA.

Justin Bohnet

[email protected]

Systems of trapped ions have made substantial progress in sim-

ulating quantum magnetic models. But as the number of spins

in the simulation increases, the number of measurements re-

quired to fully characterize the density matrix of the output

state exponentially grows. Therefore, efficient methods for mea-

suring quantum signatures are needed to effectively identify,

categorize, and quantify entangled spin states. Here we perform

quantum simulations of spin models using 9Be+ ions in a Pen-

ning trap, capable of producing entangled states in planar arrays

of hundreds of spins. To benchmark quantum effects generated

by an engineered Ising interaction, we generate spin-squeezed

states[1] and directly observe up to 6.0 dB of spectroscopic en-

hancement. In addition, we characterize over-squeezed, non-

36

Gaussian collective spin states, where spin-squeezing fails to

identify entanglement, with a more general entanglement wit-

ness using the quantum Fisher information[2]. Furthermore, we

present results from a Loschimdt echo sequence that can ob-

serve many-body spin correlations from the multiple quantum

coherence spectrum[3]. In the future, we will apply these bench-

marking techniques to simulations of non-trivial spin models,

such as the XY model and the transverse field Ising model with

variable range interactions.

Acknowledgements: NIST NRC, NSF-PHY 1521080, JILA-NSF-

PFC-1125844, ARO, MURI-AFOSR and AFOSR.

[1] J. Bohnet, et al., Science, 352, (2016).

[2] H. Strobel, et al., Science 345, (2014).

[3] A. Gonzalo, D. Suter, and R. Kaiser, Science 349, (2015).

37

Invited talk

Professor Danny Segal: his contributions toresearch with Penning traps and to the ion trap

communtity

R. C. Thompson1

1QOLS Group, Physics Department, Imperial College London,

London SW7 2AZ, UK.

Richard Thompson

[email protected]

Danny Segal, who died prematurely in 2015, was a talented

physicist, researcher and lecturer. Beyond that, he made excep-

tional contributions to his department at Imperial College Lon-

don, acting as the mentor to postgraduate students and then the

Senior Tutor, with pastoral resonsibility for 800 undergraduate

students. He was also instrumental in setting up Imperial’s in-

novative Centre for Doctoral Training programme in Controlled

Quantum Dynamics.

In the European ion trap community he was keen to get to

know other researchers and to encourage collaborations be-

tween groups. Following on from his experience coordinating

EU networks such as QUBITS, QGATES and SCALA he was a

participant in PICC and was an enthuastic organiser of the first

ECTI, held in the UK in 2010.

On the scientific side, Danny’s passion was to build up tools

for the coherent manipuation of ions in Penning traps. He initi-

ated the first laser cooling experiments with calcium ions in a

Penning trap, showing that laser cooling was achievable despite

the large number of laser frequencies required. One application

38

of this was the creation and manipulation of small ion Coulomb

crystals in a Penning trap, which he used as a live demonstration

in his inaugural lecture as Professor.

Towards the end of his life he achieved the major goal of

demonstrating ground state cooling of the axial motion of a sin-

gle ion in a Penning trap and showing that the heating rate is one

of the lowest yet achieved in any type of ion trap [1]. Coherent

effects such as Ramsey fringes and Rabi flopping could then be

observed on the optical qubit. Since then, the group has gone on

to cool the radial motion of a single ion, which is complicated

because of the unusual nature of the radial motion in a Penning

trap. The group has also successfully cooled the motion of two

ions to the ground state of both axial degrees of freedom simul-

taneously. This requires complex cooling protocols because the

motion is initially far outside the Lamb-Dicke regime.In my talk I will survey briefly Danny’s various contributions

and discuss the recent work of the group.

[1] J. G. Goodwin et al., Phys. Rev. Lett. 116, 143002 (2016)

39

Invited talk

Fast Gates and Slow Spin Models

J. Amini, E. Birckelbaw, M. Cetina, K. Collins, C. Crocker, S.

Debnath, C. Figgatt, A. Grewal, M. Hernandez, P. Hess, D. Hucul, K.

Hudek, V. Inlek, K. Johnson, H. Kaplan, K. Landsman, A. Lee, M.

Lichtman, N. Linke, J. Mizrahi, G. Pagano, P. Richerme, J. Smith, K.

Sosnova, D. Wong-Campos, K. Wright, J. Zhang, and C. Monroe

Joint Quantum Institute, Joint Center for Quantum Information and

Computer Science, and Department of Physics, University of

Maryland, College Park MD 20742 USA.

Christopher Monroe

[email protected]

Conventional quantum gates between trapped ions map qubit

information through phonons, using patterns of qubit state-

dependent forces. We present the progress on two extremes of

this idea. Ultrafast high energy last pulses allow gate operations

that are faster than the trapped ion oscillation frequencies, and

exploit the Coulomb interaction more directly without the need

for Lamb-Dicke confinement [1, 2]. Not only are these gates

much faster than conventional operations, but they should also

be less susceptible to noise sources and scalable because they

involve only local modes of motion. We present recent progress

on sub-microsecond gates and also the fast generation of very

large Schrödinger Cat states of motion. At the other extreme,

when the state-dependent forces are far-detuned and disper-

sive, the phonons can be adiabatically eliminated, resulting in

pure spin-spin Ising and XY models with tunable and long-range

interactions. This slower interaction allows quantum simula-

40

tions of magnetism, from studies of quantum dynamics [3, 4] to

quantum thermalization studies [5]. Recent experiments have

investigated the implementation of interacting spin-1 models

[6] and the study of topologically-ordered quantum states of

the spin chain. Soon these experiments will be extended to > 30

spins, where no classical computer can predict its behavior, par-

ticularly the many-body dynamics.This work is supported by the ARO with funding from

the IARPA LogiQ program, the AFOSR MURI on Quantum Trans-duction, the AFOSR MURI on Quantum Measurement, the ARLCenter for Distributed Quantum Information, the ARO AtomicPhysics Program, and the NSF PFC at JQI.

[1] J. J. Garcia-Ripoll, et al., Phys. Rev. Lett. 91, 157901 (2003).

[2] J. Mizrahi, et al., Applied Phys. B 114, 45 (2014).

[3] P. Richerme, et al., Nature 511, 198 (2014).

[4] C. Senko, et al., Science 345, 430 (2014).

[5] J. Smith et al., Nature Physics, doi10.1038/nphys3783 (2016).

[6] C. Senko, et al., Phys. Rev. X 5, 021026 (2015).

41

Invited talk

Characterizing the non-equilibrium dynamicsof ion strings with up to twenty ions simulating

Ising interactions

C. Maier1,2, T. Baumgratz3, C. Hempel1,2, P. Jurcevic1,2, B. P. Lanyon1,2,

A. Buyskikh4, A. J. Daley4, M. Cramer3, M. Plenio3,

R. Blatt1,2, C. F. Roos1,2

1Institute for Quantum Information and Quantum Optics, Austrian

Academy of Sciences, 6020 Innsbruck, Austria.2Institute for Experimental Physics, University of Innsbruck, 6020

Innsbruck, Austria.3Institute for Theoretical Physics, University of Ulm, 89069 Ulm,

Germany.4 Department of Physics, University of Strathclyde, Glasgow G4

0NG, UK.

Christian Roos

[email protected]

Strings of ions dressed with laser light can be used to simulatethe physics of long-range transverse Ising models. I will presentexperiment with up to twenty ions in which we aim to character-ize the overall quantum state of non-equilibrium states createdby subjecting an initial Néel-like state to the Ising interactions.By measuring all correlation functions of neighbouring ions, wereconstruct the quantum state by matrix-product state tomog-raphy and find lower bounds on the fidelity of the experimentalstate with the reconstructed state. We also measure the fidelityof a 14-qubit state with reconstructed state by direct fidelitymeasurements based on measuring random Pauli strings [1].

[1] C. Maier et al., manuscript in preparation.

42

Invited talk

Trapped ion spin-boson quantum simulators

D. Porras1

1 Department of Physics and Astronomy, University of Sussex,

Falmer, Brighton BN19QH, United Kingdom.

Diego Porras

[email protected]

Spin-motion couplings in trapped ions crystals lead to a variety

of fascinating many-body phases in which internal states are

entangled with vibrational modes. The regime of strong spin-

motion coupling can be used for robust quantum simulations.

Furthermore, by exploiting the vibrational modes as an active

degree of freedom, the complexity of the simulated quantum

phases increases dramatically when compared with pure spin

systems.

We have theoretically shown that a trapped ion spin-boson

chain can show highly frustrated quantum phases. Strong spin-

phonon couplings can be used in a quantum annealing protocol

to seek for the exact ground state of the system [1]. An experi-

mental implementation of our ideas would shed light on the ad-

vantages of quantum annealing for the solution of minimization

problems. Spin-boson couplings can also lead to the implemen-

tation of gauge symmetries leading to an exotic quantum phase

diagram [2].

The complexity of spin-motion phases makes trapped ioncrystals an ideal system to study non-equilibrium phenomena.In particular, an ion crystal can be used to study the thermaliza-tion of an initial excited state in a closed quantum system [3].

43

The conditions and time-scales over which quantum thermal-ization occurs are still under intense theoretical investigation. Atrapped ion crystal of only five ions already poses a challenge forexact numerical calculations, since a large number of vibrationalquantum states must be included for an accurate descriptionof non-equilibrium processes. A theoretical characterization ofthe system can be carried out by means of an effective dimen-sion that quantifies the number of quantum states involved inthe thermalization process. In a recent experiment-theory col-laboration we have been able to observe thermalization in aclosed trapped ion chain, and we have observed that the effi-ciency of this non-equilibrium process is related to the effectivedimension of the initial state [3].

[1] P. Nevado and D. Porras, Phys. Rev. A 93, 013625 (2016).

[2] P. Nevado and D. Porras, Phys. Rev. A 92, 013624 (2015).

[3] G. Clos, D. Porras, U. Warring, and T. Schätz, arXiv:1509.07712.

44

Invited talk

Rotational state-to-state collisions of coldmolecular ions

R. Wester1

1Institute for Ion Physics and Applied Physics, University of

Innsbruck, Technikerstr. 25, 6020 Innsbruck, Austria.

Roland Wester

[email protected]

In this talk I will present our investigations of cold OH− ionscolliding with helium and hydrogen, using a cryogenic radiofre-quency multipole trap [1]. Rotational state analysis by photode-tachment spectroscopy [2] was employed to measure the in-elastic scattering rate coefficient for the J = 1 to 0 rotationalquenching in OH− + He collisions [3]. The measurements arecompared with ab initio quantum scattering calculations. Fur-thermore, energy transfer from the hydrogen J = 1 rotation toOH− was observed. Rotational state analysis by photodetach-ment was also employed to perform high resolution terahertzspectroscopy on OD− and observe the two lowest rotationaltransitions [4].

[1] R. Wester, J. Phys. B 42, 154001 (2009)

[2] R. Otto, A. von Zastrow, T. Best, R. Wester, Phys. Chem. Chem. Phys.

15, 612 (2013)

[3] D. Hauser, S. Lee, F. Carelli, S. Spieler, O. Lakhmanskaya, E. S. Endres,

S. S. Kumar, F. Gianturco, R. Wester, Nature Physics 11, 467 (2015)

[4] S. Lee, D. Hauser, O. Lakhmanskaya, S. Spieler, E. S. Endres, K.

Geistlinger, S. S. Kumar, R. Wester, Phys. Rev. A 93, 032513 (2016)

45

Invited talk

Cold chemical reactions using trapped andsympathetically cooled ions

B. Heazlewood1, E. Steer1, L. Petralia1, C. Rennick1, N. Deb1,

J. Toscano1, K. Dulitz2, T. P. Softley3

1Dept. of Chemistry, University of Oxford, Chemistry Research

Laboratory, Oxford, United Kingdom.2Laboratorium für Physikalische Chemie, ETH Zürich, 8093, Zürich,

Switzerland.3University of Birmingham, Edgbaston, Birmingham, B15 2TT,

United Kingdom.

Tim Softley

[email protected]

A key objective of our research is to measure the rates and/or

cross sections for reactive ion-molecule collisions for polyatomic

species at T < 10 K and with state selected reactants. In this pre-

sentation progress towards achieving these objectives will be

discussed [1]. In our experiments we combine sympathetically-

cooled molecular ions in a Ca+ Coulomb crystal with two sources

of cold neutrals either from a Stark decelerator or from a quadrupole

guide velocity selector [1]. Decelerated molecules tend to be nat-

urally state selected, whereas the velocity-selected molecules

tend to maintain the rotational distribution of the source, for

which the temperature can be varied cryogenically.Given that reactions such as NH+3 + ND3 have multiple prod-

uct channels available e.g., charge transfer, H atom transfer orproton/deuteron transfer, it is necessary to be able to mass se-lectively detect ionic products to measure branching ratios. Theuse of trap-ejection and mass spectrometry to measure ionic

46

product branching ratios will be presented along with the latestresults from measuring reactions using the Stark deceleratorion-trap combination. The development of a Zeeman decelera-tor ion-trap combination for studying radical-ion processes willalso be discussed.

[1] B. Heazlewood and T.P. Softley , Ann. Rev. Phys. Chem. 66 475-495

(2015) .

47

Hot topic talk + Poster No. 1

A dynamic ion-atom hybrid trap forhigh-resolution cold-collision studies

A. D. Dörfler1, P. Eberle1, C. von Planta1, S. Willitsch1

1Department of Chemistry, University of Basel, 4056 Basel,

Switzerland.

Alexander Dörfler

[email protected]

We introduce a new experiment for studies of cold ion-neutralcollisions and reactions with a significantly enhanced energyresolution compared to previous experiments. Our approachis based on pushing a cloud of laser-cooled Rb atoms througha stationary Coulomb crystal of cold ions using precisely con-trolled, tunable radiation-pressure. We can presently tune theatom kinetic energies over an interval from 30 mK to 350 mK withan energy spread as low as 24 mK inferred from comparing theexperimental time-of-flight measurements to Monte Carlo tra-jectory simulations. Our development opens up possibilities foraccurate studies of the energy dependence of the reaction ratesand the dynamics and reaction-product ratios of ion-neutralprocesses in the cold regime, paving the way for the realisationof fully energy- and state-controlled cold-collision experiments.

48


Dynamics of a ground-state cooled ion collidingwith ultra-cold atoms

Z. Meir, T. Sikorsky, R. Ben-shlomi, N. Akerman, Y. Dallal,

and R. Ozeri

Department of Physics, Weizmann Institute of Science, Rehovot

7610001, Israel

Roee Ozeri

[email protected]

Understanding atom-ion collision dynamics is essential for thefield of ultra-cold atom-ion physics. In our system, we over-lap a ground-state cooled 88Sr+ ion with ultra-cold 87Rb atoms.We measure the ion energy distribution with narrow opticalclock spectroscopy after few collisions and using Doppler re-cooling thermometry in steady-state. We observe the heating ofthe ion to mK temperatures after few collisions. We also observea deviation in the energy distribution from Maxwell-Boltzmanndistribution to power-law distribution [1]. We are capable ofstudying ultra-cold physics by limiting the interaction to fewcollisions. We investigate the spin dynamics of the ion after fewcollisions with spin polarized cloud of ultra-cold atoms and wehave found that it is dominated by spin-exchange rather thanspin-orbit interaction.

[1] Z. Meir et al., arXiv:1603.01810.

49

Invited talk

High NOON State of Phonons in a Trapped IonSystem

Junhua Zhang1, Mark Um1, Dingshun Lv1, Jing-Ning Zhang1,

Lu-Ming Duan1,2, and Kihwan Kim1

1Center for Quantum Information, Institute for Interdisciplinary

Information Sciences, Tsinghua University, Beijing, 100084, P. R.

China2Department of Physics, University of Michigan, Ann Arbor,

Michigan 48109, USA

Kihwan Kim

[email protected]

Multi-party entangled state, in particular, NOON state has broughtgreat interests because it allows the precision measurement tothe ultimate limit as the number of particles increases. However,experimental preparation of the NOON state with sufficientlyhigh number of particles N remains as a challenge. Here wedevelop a deterministic method to generate the NOON state ofarbitrary phonon numbers and experimentally create the statesup to N = 9 phonons in two radial modes of a single trapped171Yb+ ion. We clearly observe the fidelity of the NOON state overclassical limit by measuring the contrast of the characteristicphase oscillations and the populations through the phonon pro-jective measurement of two motional modes. We also observethe Heisenberg scaling of phase sensitivity in the NOON statesthrough quantum Fisher information. Our scheme is genericand directly applicable to cavity QED or circuit QED systemsand optomechanical systems.

50

Invited talk

Quantum information processing and quantumsimulation based on phonons in trapped ions

K. Toyoda1 and S. Urabe1Graduate School of Engineering Science, Osaka University, Japan

Kenji Toyoda

[email protected]

Phonons in trapped-ion systems are usually used to mediate

interaction between ions, while they can also be considered as

independent degrees of freedom that may play central roles in

quantum information processing and quantum simulation [1].

We observed hopping of a radial (or transverse) phonon in

two ions in a linear trap with a relatively large distance ∼20 µm(Fig. 1). With this result, the coherence of the phonon system

was confirmed.

The relatively good coherence may enable us to observe in-

terference between phonons. Interference of two bosonic parti-

cle has been extensively studied in photonic systems and is

called the Hong-Ou-Mandel (HOM) effect. We recently suc-

ceeded in observing the phonon-counterpart of the HOM effect

using two radial phonons in a two-ion crystal [2].

Phonons can also be coupled with the internal states of ions

using a sideband transition to form a Jaynes-Cummings (JC)

system, and an interconnected array of JC systems is formed

when phonons are allowed to hop between ion sites [Jaynes-

Cummings-Hubbard (JCH) model]. The JCH model has a simi-

larity to the Bose-Hubbard model and is related to interacting

51

electrons in solid state materials. We would also like to mention

our recent progress in quantum simulation of the JCH model

using trapped ions [3].

Fig. 1: Hopping of a radial phonon between two ion sites.

[1] D. Porras and J. I. Cirac, Phys. Rev. Lett. 93, 263602 (2004); C. Shen

et al., Phys. Rev. Lett. 112, 050504 (2014).

[2] K. Toyoda et al., Nature 527, 74 (2015).

[3] K. Toyoda et al., Phys. Rev. Lett. 111, 160501 (2013).

52


Refocusing two qubit gates with measurementsfor trapped ions

T. Gefen1, D. Cohen1, I. Cohen1, A. Retzker1

1Racah Institute of Physics, The Hebrew University of Jerusalem,

Jerusalem 91904, Givat Ram, Israel.

Alex Retzker

[email protected]

Dynamical decoupling techniques are the method of choice forincreasing gate fidelities. While these methods have producedvery impressive results in terms of decreasing local noise andincreasing the fidelities of single qubit operations, dealing withthe noise of two qubit gates has proven more challenging. Themain obstacle is that the noise time scale is shorter than thetwo qubit gate itself so that refocusing methods do not work.In this talk I will present a measurement and feedback basedmethod to refocus two qubit gates which cannot be refocusedby conventional methods. I will show that this scheme couldpotentially reduce the fault tollerant threshold for trapped ionsquantum computing by two orders of magnitude [1].

[1] T. Gefen et al., arXiv:1604.05944.

53


Quantum nondemolition parity measurementand Bayesian-assisted techniques in a

mixed-species ion crystal

V. Negnevitsky1, H.-Y. Lo1, M. Marinelli1, C. Flühmann1, R. Oswald1,

J. P. Home1

1Institute for Quantum Electronics, ETH Zürich, 8093, Zürich,

Switzerland.

Vlad Negnevitsky

[email protected]

Quantum nondemolition measurements are a critical elementof feedback-based quantum error correction, as well as a power-ful building block in more general QIP and metrology protocols.We have carried out a nondemolition parity measurement oftwo beryllium ions via a calcium ion in the same trap, relyingon mixed-species entangling gates and local operations imple-mented using global laser beams. We have characterized theoperation of the technique on a range of Bell states. We alsopresent real-time Bayesian techniques which we have separatelyused to improve state detection and phase estimation speed.Our work offers several advantages over standard methods ashybrid trapped-ion QIP systems grow in complexity.

54

Evening lecture

The Jaynes-Cummings Hamiltonian inTrapped-Ion Physics

R. Blatt1,2

1 Institut f. Experimentalphysik, Universität Innsbruck,

Technikerstrasse 25, A-6020 Innsbruck, Austria2 Institut f. Quantenoptik und Quanteninformation,

Österreichische Akademie der Wissenschaften,

Technikerstrasse 21a, A-6020 Innsbruck, Austria

Rainer Blatt

[email protected]

The development of trapped ion physics in the 1990s and early

2000s will be reviewed and key experiments will be highlighted.

55

Invited talk

Precision measurements of fundamentalproperties of atomic particles in Penning traps

K. Blaum1

1Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117

Heidelberg, Germany.

Klaus Blaum

[email protected]

This contribution will provide an overview on recent applica-tions of precision measurements with cooled and stored ions inPenning traps. On the one hand, precision Penning-trap massmeasurements provide indispensable information for atomic,nuclear and neutrino physics as well as for testing fundamentalsymmetries [1, 2]. On the other hand, in-trap measurements ofthe bound-electron g-factor in highly-charged hydrogen-likeions allow for better determination of fundamental constantsand for constraining Quantum Electrodynamics (QED) [3, 4, 5].Furthermore, ongoing preparations for the experimental com-parison of the proton and antiproton g-factors will allow us toachieve a crucial test of the Charge-Parity-Time reversal (CPT)symmetry [5, 4]. Among others a 13-fold improvement of theatomic mass of the electron by combining a very accurate mea-surement of the magnetic moment of a single electron boundto a carbon nucleus with a state-of-the-art calculation in theframework of bound-state QED [4] as well as the most stringenttest of CPT symmetry on the baryonic sector by a charge-to-mass ratio comparison of the proton and antiproton [2] will bepresented.

[1] E.G. Myers et al., Phys. Rev. Lett. 114, 013003 (2015).

56

[2] S. Eliseev et al., Phys. Rev. Lett. 115, 062501 (2015).

[3] S. Sturm et al., Phys. Rev. Lett. 107, 023002 (2011).

[4] S. Sturm et al., Nature 506, 467 (2014).

[5] F. Köhler et al., Nature Comm. 7, 10246 (2016).

[6] J. DiSciacca et al., Phys. Rev. Lett. 110, 130801 (2013).

[7] A. Mooser et al., Nature 509, 597 (2014).

[8] S. Ulmer et al., Nature 524, 196 (2015).

57

Invited talk

High-Precision Comparisons of theFundamental Properties of the Proton and the

Antiproton

S. Ulmer1 − for the BASE collaboration1Ulmer Initiative Research Unit, RIKEN, 351-0198, Saitama, Japan.

Stefan Ulmer

[email protected]

Our current understanding of the Universe comes, among oth-ers, from particle physics and cosmology. In particle physics,the Standard Model (SM) implies a perfect symmetry betweenmatter and antimatter conjugates. On cosmological scales, how-ever, a striking matter/antimatter imbalance is observed. Thisdiscrepancy has yet to be understood and inspires comparisonsof the fundamental properties of particles and antiparticles withhighest precision. The BASE collaboration at the Antiproton De-celerator (AD) of CERN targets both, the high-precision compar-ison of the antiproton-to-proton charge-to-mass ratios as well asthe comparison of the g-factors of these two matter/antimatterconjugates. Our experiments are based on single particle spec-troscopy in an advanced Penning-trap system [1]. By comparingthe cyclotron frequencies of single antiprotons and negativelycharged hydrogen ions with high sampling rate we performedvery recently the most precise comparison of the charge-to-mass ratios of the two particles with a fractional precision of69 ppt [2]. Our result is consistent with the charge-parity-time(CPT) invariance of the SM and constitutes the most stringentdirect test of CPT symmetry with baryons to date. Currently weare focussing on the much more difficult measurement of theantiproton g -factor with ppb precision. To this end we apply the

58

methods developed for our 3.3 ppb measurement of the protong -factor [3, 4] to the antiproton. Compared to previous results[5] the targeted measurement will constitute a thousand-foldimproved test of CPT invariance using a baryonic vector quan-tity. In the talk the BASE-results produced so far are summarizedand the current status of the experiment is being discussed.

[1] Smorra, C. et al., Eur. Phys. J. S.T. 224, 3055 (2015).

[2] Ulmer, S. et al., Nature 524, 196 (2015).

[3] Ulmer, S. et al., Phys. Rev. Lett. 106, 253001 (2011).

[4] Mooser, A. et al., Nature 509, 596 (2014).

[5] DiSciacca, J. et al., Phys. Rev. Lett. 110, 130801 (2013).

59

Invited talk

Search for new physics with highly charged ions

M. S. Safronova

Department of Physics and Astronomy, University of Delaware,

Newark, Delaware, USA and Joint Quantum Institute, NIST and the

University of Maryland, Gaithersburg, Maryland, USA

Marianna Safronova

[email protected]

In many theories beyond the Standard Model of elementary

particles and general relativity dimensionless fundamental con-

stants become dynamic fields. Such theories include string theo-

ries, discrete quantum gravity and loop quantum gravity, chameleon

models, quintessence (dark energy) models, and others. The

search for the variation of the fundamental constants is also a

test of the local position invariance hypothesis and thus of the

equivalence principle.

Selected forbidden transitions in highly charged ions (HCI)

were shown to have very large sensitivities to the possible vari-

ation of the fine-structure constant α. Moreover, some highly

charged ions have level structure and other properties that are

not present in any neutral and low-ionization state ions that

may be advantageous for the development of atomic clocks and

provide remarkable new opportunities for precision tests of fun-

damental science and quantum information. One of the main

obstacles for the experimental work in this direction is the lack

of experimental data for these systems as well as difficulties in

accurate theoretical predictions of the transition wavelengths.

We carried out an exhaustive search of transitions in highly

60

charged ions that are particulary well suited for the experimen-

tal exploration [1]. We identified HCIs that have all features of

the best optical clock transitions leading to possibility of the

frequency measurements with fractional accuracy on the level

of 10−18 or better and have a factor of 100 extra enhancement

of α-variation in comparisons to experimental frequency ratio

measurement accuracy [2].Proposal for tests of Lorentz symmetry [2] with Yb+ and

highly charged ions are also presented.

[1] M. S. Safronova, V. A. Dzuba, V. V. Flambaum, U. I. Safronova, S. G.

Porsev, and M. G. Kozlov, Phys. Rev. Lett., 113, 030801 (2014).

[2] V. A. Dzuba, M. S. Safronova, U. I. Safronova, and V. V. Flambaum,

Phys. Rev. A 92, 060502(R) (2015).

[3] V. A. Dzuba, V. V. Flambaum, M. S. Safronova, S. G. Porsev, T. Prut-

tivarasin, M. A. Hohensee, and H. Häffner, Nature Physics 12, 465

(2016).

61

Invited talk

Experiments with stored ion beams at theDESIREE facility in Stockholm

H. Cederquist1

1Physics Department, Stockholm University, AlbaNova university

center, S 10691, Stockholm, Sweden.

Henrik Cederquist

[email protected]

In this talk I am going to describe some of the recent experimentsand tests performed with stored ion beams at the DESIREE fa-cility [1, 2] at Stockholm University. DESIREE stands for DoubleElectroStatic Ion Ring ExpEriment and as the name suggestsit has two electrostatic ion storage rings with a common ion-beams merging section where two stored beams may be mergedfor studies of ion-ion collisions at very low energies. The ionrings are cryogenically cooled and operated at temperaturesdown to 11–12 Kelvin. Because the rings are electrostatic ions ofany mass or type may be stored including protons, heavy clus-ter ions, biomolecular ions, fullerene ions etcetera. Because theion storage rings, and the chamber in which they are mounted,are operated at cryogenic temperatures, the stored ions will re-lax towards their lowest quantum states allowing for quantumstate resolved studies of inherent ion properties and reactionprocesses. I will discuss preliminary results in which OH- molec-ular ions are stored for long times and in which the populationis strongly dominated by the lowest rotational state, J=0, afterminutes of storage in one of the rings. I will also discuss mea-surements of lifetimes of long-lived (seconds and minutes [3])excited states in atomic anions, cooling of metal cluster anions,and give a progress report on our work on collisions between

62

anions and cations in the sub-eV collision energy range. Thecircumferences of the ion-storage rings are 8.6-meters. Pulsedand cw lasers may be merged or crossed with the stored ionbeams for various experimental investigations.

[1] R.D. Thomas et al., Review of Scientific Instruments 82, 065112

(2011).

[2] H.T. Schmidt et al., Review of Scientific Instruments 84, 055115

(2013).

[3] E. Bäckström et al., Phys. Rev. Lett. 114, 143003 (2015).

63

Invited talk

The role of internal rotation in atom-moleculecollisions: Sympathetic cooling and cold

reactions

Christiane P. Koch1

1Theoretische Physik, Universität Kassel, Heinrich-Plett-Str. 40,

34132 Kassel, Germany.

Christiane Koch

[email protected]

Cooling molecular ions is an essential prerequisite for their ap-

plication in precision measurements, quantum information pro-

cessing, or controlled chemistry. Sympathetic cooling of molecu-

lar ions by collisions with laser cooled atoms is a viable route [1].

Its efficiency may be hampered, however, by rotationally in-

elastic collisions [2]. We estimate the probability of changing

the rotational state of a diatomic molecular ion in a collision

with a laser-cooled atomic ion, treating the latter in terms of the

Coulomb force it exerts on the molecule. We find the dynamics

to be entirely different for polar compared to non-polar molec-

ular ions and discuss the prospects for sympathetic cooling as a

function of the reduced mass and the rotational splitting of the

molecule.While preservation of the internal rotational state of the

molecule is a target in sympathetic cooling, choice of this statebecomes a control knob in cold reactive collisions. We demon-strate its importance for the dynamics of Penning ionizationreactions and show how the quantum state of the molecularrotor determines the role of anisotropy in the reactive atom-molecule collisions: For fast reactions, which are governed by

64

the long-range forces, we observe rotational state-dependentuniversal scaling laws for the reaction rate coefficient as a func-tion of collision energy [3], whereas for slow reactions, which aredominated by quantum resonances, the internal rotational statecan be used to switch the anisotropic part of the interaction onor off [4].

[1] K. Mølhave and M. Drewsen, Phys. Rev. A 61, 011401 (2000)

[2] D. Hauser et al., Nature Physics 11, 467 (2015)

[3] Y. Shagam et al., Nature Chemistry 7, 921 (2015)

[4] A. Klein et al., arXiv:1606.04384 (2016)

65

Invited talk

Rotation of cold molecular ions inside aBose-Einstein condensate

B. Midya1, M. Tomza2, R. Schmidt3,4, M. Lemeshko1

1Institute of Science and Technology Austria, Am Campus 1, 3400

Klosterneuburg, Austria.2ICFO-Institut de Ciències Fotòniques, The Barcelona Institute of

Science and Technology, Barcelona, Spain.3ITAMP, Havard-Smithsonian Center for Astrophysics, Cambridge,

MA 02138, USA.4Physics Department, Harvard University, 17 Oxford Street,

Cambridge, MA 02138, USA.

Mikhail Lemeshko

[email protected]

Recently we have developed a theory describing a rotating im-purity − such as a cold molecule − coupled to a Bose-Einsteincondensate (BEC). It was shown that in such a setting the impu-rity rotational motion becomes dressed by a field of many-bodyexcitations, giving rise to quasiparticles of a new kind − the ‘an-gulons’ [1, 2]. Here we use accurate ab initio potential energysurfaces to demonstrate that angulons can be detected and stud-ied in modern experiments on cold molecular ions immersedinto a BEC [3]. While we exemplify the theory with a CN− anionin a BEC of Rb and Sr, the effects are not expected to changequalitatively or quantitatively for positive molecular ions. Thisopens up a new avenue to simulate complex many-body statesof matter using cold molecular ions which has been challengingso far.

[1] R. Schmidt, M. Lemeshko, Phys. Rev. Lett. 114, 203001 (2015).

66

[2] R. Schmidt, M. Lemeshko, Phys. Rev. X 6, 011012 (2016).

[3] B. Midya, M. Tomza, R. Schmidt, M. Lemeshko, arXiv:1607.06092

(2016).

67

Invited talk

Spectroscopy of Trapped, Mobility-Selected,Biomolecular Ions

T. R. Rizzo1

1Laboratoire de Chimie Physique Moléculaire, École Polytechnique

Fédérale de Lausanne, EPFL SB ISIC LCPM, Station 6, CH-1015

Lausanne, Switzerland.

Thomas Rizzo

[email protected]

Over the last number of years we have used cryogenic ion spec-

troscopy to investigate the structures of biomolecular ions in the

gas phase. As one applies this approach to molecules of increas-

ing complexity, it becomes more difficult to resolve individual

conformations spectroscopically, and this inhibits our ability to

measure conformation-specific vibrational spectra and hence

to determine structure. From the theoretical side, the confor-

mational search space for larger molecules becomes difficult

to sample exhaustively, inhibiting our ability to find the lowest

energy structures.

To be able to further simplify complex spectra and to help the

conformational search process, we have combined cryogenic

ion spectroscopy with ion mobility. This combined approach al-

lows us to sort conformations of molecules by their drift time in

helium and inject only one or a subset of them into the cold ion

trap. Moreover, the orientationally averaged cross-section that

we obtain from the drift time helps narrow the conformational

search-space by adding additional constraints on the calculated

68

structures.

We describe our recently constructed hybrid instrument,

which consists of a segmented, ion-mobility drift-tube coupled

to a newly designed, cryogenic, planar ion trap, which is in turn

coupled to a time-of-flight mass spectrometer. After selecting

ions with a particular drift time, we tag them with D2 molecules

in the cold trap and then measure vibrational spectra by detect-

ing the detachment of D2 as a function of the IR laser wavenum-

ber.

We show a series of experiments on small peptides that demon-strate our ability to selectively inject ions into our ion trap thathave been separated by their drift time. We also demonstratehow we can intentionally isomerize molecules by collisionallyactivating them in the drift tube, which helps determine whichconformations may be kinetically trapped from solution.

69

Invited talk

Molecular Rotation of very floppy molecules, thecase of CH+5

H. Schmiedt1, P. Jensen2, O. Asvany1, S. Brackertz1, S. Schlemmer1

1I. Physikalische Institut, Universität zu Köln, Germany.2Physikalische und Theoretische Chemie, Fakultät für Mathematik

und Naturwissenschaften, Bergische Universität Wuppertal,

Germany.

Stephan Schlemmer

[email protected]

Light Induced Reactions (LIR) in cryogenic traps are used torecord action spectra of electronic, vibrational, and pure rota-tional transitions of many molecular ions. One example con-cerns the enigmatic CH+5 molecule, protonated methane. Thismolecule exhibits large amplitude motions in almost all degreesof freedom and therefore the ro-vibrational spectrum in therange of C-H stretching vibrations contains thousands of lineseven at T = 10 K. The challenge of these complex spectra is to un-derstand the rotational motion in this very fluxional molecule,whose large amplitude motions can not be frozen at even lowertemperatures. The line centers of the measured transitions aredetermined with an accuracy of better than 1 MHz in most casesby calibration against a frequency-comb. Based on this veryhigh-precision measurements we started to reconstruct the lowenergy term diagram based on ground state combination differ-ences [1]. These term diagrams are related to the lowest energyrotational and vibrational modes of the molecule. We presenta model of collective molecular rotation which combines theend-over-end rotation with the internal rotation in this very flux-ional molecule. The zeroth order model leads to a very simple,

70

algebraic energy relation. The corresponding energy levels agreevery well with the experimentally found values. In conclusionthere is strong evidence for collective rotational motions, i.e.rotations in higher dimensions, in very floppy molecules likeCH+5 .

[1] O. Asvany, K. M. T. Yamada, S. Brünken, A. Potapov, and S. Schlem-

mer, Science 347, 1346 (2015).

71

Invited talk

Ion Microsolvation Probed by Cryogenic IonTrap Vibrational Spectroscopy

Knut R. Asmis1

1Wilhelm-Ostwald-Institut für Physikalische und Theoretische

Chemie, Univeristät Leipzig, Linnéstr. 2, 04109 Leipzig, Germany.

Knut Asmis

[email protected]

How ions are solvated in solution has intrigued physical chemistssince the development of the theory of electrolytic dissociationat the end of the nineteenth century. A molecular-level under-standing of ion solvation is not only important for understand-ing chemical processes in solution, but also plays an impor-tant role in understanding the surface speciation and reactivityof aerosols. Infrared photodissociation (IRPD) spectroscopy ofmass-selected ions, thermalized to cryogenic temperatures, al-lows for a detailed characterization of the influence of the step-wise solvation of an ion on its properties, one solvent moleculeat a time. Recent advances in the vibrational spectroscopy ofmicrohydrated sulfate dianions and protonated water clustersare highlighted, with particular emphasis on the importance ofprobing a broad spectral range and of considering anharmonicas well as nuclear quantum effects to unambiguously identifythe signal carrier.

72


Using trapped ions, cryogenic spectroscopy, andion mobility to sequence carbohydrates

C. Masellis1, T. Rizzo1

1Laboratory of Molecular Physical Chemistry - LCPM, EPFL, 1015,

Lausanne, Switzerland.

Chiara Masellis

[email protected]

Our research group uses techniques and instruments normallyapplied in molecular physics to investigate the intrinsic struc-ture of biological molecules in the gas-phase. By trapping ionsin a planar cryogenic trap, and by using a combination of ionmobility and hydrogen tagging spectroscopy, we aim to builda database of collisional cross sections and spectroscopic fin-gerprints to allow the identification of carbohydrates. Sequenceidentification of these biopolymers is an important task thatcannot be addressed using the currently available mass spec-trometry techniques, since carbohydrates are made of isobaricbuilding blocks. Ion mobility, in conjunction with spectroscopy,should be able to uniquely characterize polysaccharides in or-der to allow identification of carbohydrates present in unknownsamples.

73


Observation of trap effects, EIT, and STIRAPwith a single Rydberg ion

G. Higgins1, F. Pokorny1, C. Zhang1, Q. Bodart1, W. Li,2,

I. Lesanovsky2, M. Hennrich1

1Department of Physics, Stockholm University, S-10691 Stockholm,

Sweden.2School of Physics and Astronomy, The University of Nottingham

NG7 2RD, UK.

Markus Hennrich

[email protected]

Trapped Rydberg ions are a novel approach to quantum infor-mation processing. This idea combines qubit rotations in theions’ ground states with entanglement operations via the Ry-dberg interaction. Importantly, the combination of quantumoperations in ground and Rydberg states requires the Rydbergexcitation to be controlled coherently. – In the experimentspresented here a trapped strontium ion was excited from themetastable 4D to Rydberg states. The electric trapping fieldsgive rise to phenomena which are not usually observed withneutral Rydberg atoms. For higher angular momentum statesthis includes quadrupole shift and Floquet sidebands, whichwe observed in the excitation spectra of Rydberg D states. Also,in two-photon Rydberg excitation of 42S we recently observedEIT, and mapped the population to the Rydberg state and backvia STIRAP – to our knowledge the first observed coherentlymanipulated Rydberg excitation of an ion.

74

Invited talk

Quantum logic with molecular ions

F. Wolf1, Y. Wan1, J. C. Heip1, F. Gebert1, C. Shi1, P. O. Schmidt1,2

1Physikalisch-Technische Bundesanstalt Braunschweig, 38116

Braunschweig, Germany2Institut für Quantenoptik, Leibniz Universität Hannover, 30167

Hannover, Germany

Piet Schmidt

[email protected]

Precision spectroscopy is a driving force for the developmentof our physical understanding. However, only few atomic andmolecular systems of interest have been accessible for precisionspectroscopy in the past, since they miss a suitable transition forlaser cooling and internal state detection. This restriction can beovercome in trapped ions through quantum logic spectroscopy[1, 2]. Coherent laser manipulation originally developed in thecontext of quantum information processing with trapped ionsallow the combination of the special spectroscopic propertiesof one ion species (spectroscopy ion) with the excellent con-trol over another species (logic or cooling ion). The motion oftrapped molecular ions can be efficiently cooled to the groundstate via sympathetic cooling through a co-trapped cooling ion[3]. We show how the internal state of a molecular ion can bedetected non-destructively on the cooling ion by implementinga quantum logic algorithm involving only coherent laser manip-ulation on the molecular ion [4]. An optical dipole force tuned tonear one of the molecule’s resonances interacts with the molec-ular ion only if it is in a specific state. The resulting change in themotional state of a two-ion crystal formed by the molecular andatomic ion can be efficiently detected through the latter. More

75

specifically, we detect if the MgH+ molecule is in the rotationalstate J = 1 in the vibrational and electronic ground state. Weobserve quantum jumps into and out of this state that are drivenby ambient black-body radiation. The detuning dependence ofthe dipole force is used to perform spectroscopy on an elec-tronic transition. The non-destructive internal state detectionrepresents a first step towards extending the exquisite controlachieved over selected atomic species to much more complexmolecular ions. In particular, it will allow spectroscopy of opticaltransitions in molecular ions with a resolution comparable tothat already achieved with atomic ions [2].

[1] P. O. Schmidt et al., Science 309, 749 (2005).

[2] T. Rosenband et al., Science 319, 1808 (2008).

[3] Y. Wan et al., Phys. Rev. A 91, 043425 (2015).

[4] F. Wolf et al., Nature 530, 457 (2016).

76


Preparation and coherent manipulation of purequantum states of a single molecular ion

C. W. Chou1, C. Kurz1, D. B. Hume1, P. N. Plessow2, D. R. Leibrandt1,

D. Leibfried1

1National Institute of Standards and Technology, Boulder, Colorado,

USA2Karlsruhe Institute of Technology, Karlsruhe, Germany

Chin-wen Chou

[email protected]

We demonstrate quantum control of individual molecules viaquantum logic spectroscopy [1]. In our experiment, we drivethe motional sidebands of Raman transitions in a molecularion and detect the resulting excitation of the secular motionwith a co-trapped atomic ion. This measurement projects themolecule into a pure internal state. The state of the moleculecan subsequently be coherently manipulated, as demonstratedby Rabi oscillations between magnetic sublevels of rotationalstates. We use only one far off-resonant continuous-wave laser tomanipulate the molecule. This makes our approach applicableto coherent control and precision measurement of a vast classof molecular ions.

[1] D. Leibfried, New J. Phys. 14, 023029 (2012), and references therein.

77


Search for violations of the equivalenceprinciple with 171Yb+ single-ion clocks and a 87Sr

lattice clock

N. Huntemann1, C. Sanner1, B. Lipphardt1, S. Dörscher1,

A. Al-Masoudi1, St. Falke1, N. Lemke1, S. Häfner1, C. Grebing1,

U. Sterr1, C. Lisdat1, Chr. Tamm1, E. Peik1

1Physikalisch-Technische Bundesanstalt, 38116 Braunschweig,

Germany.

Nils Huntemann

[email protected]

We report on direct comparisons of different optical clocks: asingle 171Yb+ ion clock that realizes the 2S1/2→ 2F7/2 electric oc-tupole transition frequency νE3 [1] and an optical lattice clockbased on the 1S0 → 3P0 transition of 87Sr [2]. The large sensi-tivity of νE3 to the value of the fine structure constant αmakescomparisons of these clocks suitable for a search for temporalvariations of α and a coupling of α to gravity. With data fromtwo measurement campaigns separated by 2.5 years, we canprovide the most stringent limits for violations of both funda-mental principles. Furthermore, the data can be used to improveprevious tests of Lorentz symmetry.

[1] N. Huntemann et al., Phys. Rev. Lett. 116, 063001 (2016).

[2] C. Grebing et al., Optica 3, 563 (2016).

78


Quantum Algorithms on a ProgrammableQuantum Computer

N. M. Linke1, S. Debnath1, C. Figgatt1, K. A. Landsman1, K. Wright1,

C. Monroe1

1Joint Quantum Institute, UMD and NIST, College Park, Maryland

20742.

Norbert Linke

[email protected]

We present a modular quantum computing architecture basedon a chain of 171Yb+ ions with individual Raman beam address-ing and readout [1]. Using a pulse-shaping scheme [2] we pro-duce entangling gates between all qubit pairs. This creates afully connected system

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