quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have...
TRANSCRIPT
![Page 1: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/1.jpg)
Quantum engineering:
Theory, design and promise of quantum
coherent macroscopic structures
Alexandre Zagoskin
Department of Physics
Loughborough University
September 15, 2015
![Page 2: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/2.jpg)
My background
http://journal.frontiersin.org/journal/ict/section/
quantum-computing
![Page 3: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/3.jpg)
• The fabrication and control of macroscopic artificial quantum structures, such as qubits, qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick evolution from theoretical musings to what can now be called quantum engineering. The development of this discipline will play the decisive role in the “second quantum revolution”.
![Page 4: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/4.jpg)
What is “engineering”?
• Accommodating incompatible requirements
• Using “rule-of-thumb” estimates for characterizing and predicting the system’s performance and reliability
• Heuristics
• Scaling
• “Engineering is about building reliable structures using non-reliable components”
![Page 5: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/5.jpg)
Engineering
UNIT ENGINEERING
STRUCTURAL ENGINEERING
SYSTEMS ENGINEERING
![Page 6: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/6.jpg)
First quantum revolution
• Semiconductors
▫ Tunnelling
▫ Band theory
• Lasers
▫ Photon – atom interactions
▫ Rate equations
• Superconductors
▫ Cooper effect
▫ Josephson effect
![Page 7: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/7.jpg)
First quantum revolution
• did not produce macroscopic quantum coherent systems
▫ quantum superpositions and entanglement in these systems involve only a small number of microscopic quantum states
![Page 8: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/8.jpg)
Philosophy of quantum mechanics • Copenhagen interpretation
• Many worlds
• Environmental decoherence
• Consistent histories
• Pilot wave
• ?
• “Shut up and calculate!”
![Page 9: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/9.jpg)
…and all that Capra • All popularizations of quantum mechanics are
wrong • Some are much more wrong than others
• “Amount of knowledge the ancients did not possess was obviously very significant”
Attributed to Mark Twain
![Page 10: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/10.jpg)
Philosophy:
baggage train of science • …which is indispensable, but should never ever
be in the lead
![Page 11: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/11.jpg)
Copenhagen vs. Schengen
quantum-classical boundary
![Page 12: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/12.jpg)
Second quantum revolution
• Use of essentially quantum properties of macroscopic quantum coherent devices
▫ Entanglement
▫ Quantum superposition
▫ Quantum coherences
![Page 13: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/13.jpg)
Richard Feynman (1918 – 1988)
• Path integral formulation: relates quantum to classical mechanics via variational principle
Heron – Fermat – Lagrange – Hamilton – Dirac
)](),([exp)()2,1(
txtxSitDxA
1
2
![Page 14: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/14.jpg)
Richard Feynman (1918 – 1988)
• Path integral formulation: relates quantum to classical mechanics via variational principle
Heron – Fermat – Lagrange – Hamilton – Dirac
)](),([exp)()2,1(
txtxSitDxA
1
2
![Page 15: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/15.jpg)
Richard Feynman (1918 – 1988)
• Path integral formulation: relates quantum to classical mechanics via variational principle
Heron – Fermat – Lagrange – Hamilton – Dirac
)](),([exp)()2,1(
txtxSitDxA
1
2
![Page 16: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/16.jpg)
Richard Feynman (1918 – 1988)
• An efficient modelling of a quantum system by classical means is IMPOSSIBLE
)](),([exp)()2,1(
txtxSitDxA
1
2
![Page 17: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/17.jpg)
“Standard” quantum computing
• Precise single and two-qubit quantum manipulations
• Qubit lifetime much shorter than the computational run
• Ergo:
▫ Quantum error correction
▫ Ancilla qubits, additional operations
▫ More noise, shorter lifetime
▫ Topological protection etc promising, but…
![Page 18: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/18.jpg)
On s’engage et puis on voit
![Page 19: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/19.jpg)
Why superconducting Josephson
qubits? • Energy gap suppresses decoherence due to
quasiparticles
• Superconducting phase is a macroscopic quantum variable related to directly observable quantities: electric charge (Cooper pairs’ number) and current
![Page 20: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/20.jpg)
Josephson effect: an Übercrash course
![Page 21: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/21.jpg)
Superconducting qubits
From Zagoskin & Blais, “Superconducting qubits”, Physics in Canada, Dec 2007
![Page 22: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/22.jpg)
Digression: How catty are the qubits? • How to distinguish a linear superposition from a
mixture? ▫ Take N’ identical bosons and compute reduced density
matrix for NN’ ▫ Reduced entropy SN = -tr ρN ln ρN
▫ δN = SN /min(M) (SM + SN-M) ▫ “Disconnectivity” D is the largest integer N for which
δN is smaller than some small a ▫ For 2 bosons:
product state: D=1 mixture: D=1 linear superposition: D=2
Leggett, Suppl. Prog. Theor. Phys. 69 (1980) 80-100
![Page 23: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/23.jpg)
Digression: How catty are the qubits? • Supercurrent per se is not “catty”
▫ E.g., Josephson effect
▫ We need rather (“crudely and schematically”)
Leggett, Suppl. Prog. Theor. Phys. 69 (1980) 80-100
NRLRL bajbjaAN ~)()(),...2,1(
NR
N
L baN ~),...2,1(
![Page 24: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/24.jpg)
Charge qubits
• Superposition of states with N and N+1 Cooper pairs
▫ Only two one-particle states differ
▫ D~2
![Page 25: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/25.jpg)
Flux qubits
• One island’s phase is fixed, two are in a superposition of states with different phases:
▫ Number of one-particle states involved:
NNbaN 21~),...2,1(
10322 10~0.1μ.μm1μm10cm10~~
enN
![Page 26: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/26.jpg)
QED with superconducting qubits
From Zagoskin & Blais, “Superconducting qubits”, Physics in Canada, Dec 2007
![Page 27: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/27.jpg)
M. Grajcar et al., Phys. Rev. Lett. 96, 047006 (2006);
P.J. Love et al., Quant. Inf. Proc. 6, 187 (2007).
![Page 28: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/28.jpg)
QED with superconducting qubits
From Zagoskin & Blais, “Superconducting qubits”, Physics in Canada, Dec 2007
![Page 29: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/29.jpg)
S.H.W. van de Ploeg et al., Phys. Rev. Lett. 98, 057004 (2007)
![Page 30: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/30.jpg)
S.H.W. van de Ploeg et al., Phys. Rev. Lett. 98, 057004 (2007)
![Page 31: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/31.jpg)
QED with superconducting qubits
![Page 32: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/32.jpg)
Sources of decoherence
• Intrinsic noise
▫ Thermal (quasiparticles in JJ and substrate)
▫ 1/f noise
• External noise
▫ Ambient EM fields
▫ Control and readout circuits
![Page 33: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/33.jpg)
1/f noise: two-level systems
• Using TLS for quantum information processing
Zagoskin, Ashhab, Johansson & Nori, PRL 97 (2006) 07001
![Page 34: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/34.jpg)
Using TLS for quantum information
processing
• Decoherence time is ~Tqb, not ~Tqb/N
Zagoskin, Ashhab, Johansson & Nori, PRL 97 (2006) 07001
![Page 35: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/35.jpg)
Using TLS for quantum information
processing: first experimental
realization
Neely et al., Nature Physics 4 (2008) 523
![Page 36: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/36.jpg)
Using TLS for quantum information
processing: first experimental
realization
Neely et al., Nature Physics 4 (2008) 523
![Page 37: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/37.jpg)
Neely et al., Nature Physics 4 (2008) 523
![Page 38: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/38.jpg)
Drastic improvement in quality of
superconducting qubits • 1999 – <10 ns
• 2015 – >100 µs
• manipulation time - nanoseconds
![Page 39: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/39.jpg)
…still short of what is needed for a
universal digital quantum computer
![Page 40: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/40.jpg)
![Page 41: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/41.jpg)
Quantum Slide Rules:
Adiabatic quantum computing
𝐻 𝜆 = 𝐻𝑖 1 − 𝜆 + 𝐻𝑓 𝜆
![Page 42: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/42.jpg)
![Page 43: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/43.jpg)
![Page 44: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/44.jpg)
Van der Ploeg et al., ASC 2006; A. Izmalkov et al., Europhys. Lett. 76 (2006) 533
![Page 45: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/45.jpg)
Approximate AQC – a possible
application?
![Page 46: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/46.jpg)
Feedback-controlled adiabatic
quantum computation
R.D. Wilson, A.M. Zagoskin, S. Savel’ev, and M.J. Everitt; Franco Nori (2012)
![Page 47: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/47.jpg)
![Page 48: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/48.jpg)
How far do we get from the initial
state? • “LZ diffusion”
N – number of anticrossings
per energy level
![Page 49: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/49.jpg)
From single qubits to Schrödinger’s
elephants
Charge qubits: Yamamoto
et al., 2003
Phase qubit: Allman et al., 2010
Flux qubits: Grajcar et al.,
2006
![Page 50: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/50.jpg)
![Page 51: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/51.jpg)
D-Wave controversy
![Page 52: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/52.jpg)
D-Wave controversy
• World’s biggest collection of qubits ▫ Current version of D-Wave 2X had 1152 qubits, 1097 operational
• Quantum operation confirmed for 8-qubit register • Operation consistent with both quantum and classical models • Decoherence time of a qubit much shorter than the adiabatic
evolution time • How to tell whether it is quantum, and if so, is it quantum
enough? • 3000× SNAFU • Recent data (C. Williams at Oxford): N-qubit system with E
couplers stays within 𝑁 + 𝐸 from the ground state – consistent with the LZ diffusion picture
• Latest: King et al., “TTT-benchmarking” – faster than conventional algorithms on classical computers
![Page 53: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/53.jpg)
Late
st
genera
tion C
him
aera
C1
2
Kin
g e
t al. a
rxiv
1508.0
5087
![Page 54: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/54.jpg)
“Time-To-Target” – essentially the
same approach as AAQC • How fast another algorithm can produce the
same degree of accuracy (King et al. arxiv 1508.05087)
• BUT:
▫ DOES IT REALLY MATTER?
▫ “Speed-up” is – scientifically – a minor and ill-defined question compared to the one of “degree of quantumness”
![Page 55: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/55.jpg)
![Page 56: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/56.jpg)
Wang L, Roennow T, Boixo S, Isakov S,
Wang Z, Wecker D, et al. Comment on:
“Classical signature of quantum
annealing.” arXiv:1305.5837 (2013).
![Page 57: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/57.jpg)
Shin S, Smith G, Smolin J, Vazirani U. How
“Quantum” is the D-Wave machine?
arXiv:1401.7087 (2014).
![Page 58: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/58.jpg)
Grand Challenge
![Page 59: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/59.jpg)
Grand Challenge
![Page 60: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/60.jpg)
Why now?
• Fabrication of multiqubit arrays with controlled macroscopic quantum coherence now possible
• Current theoretical methods at their limit and new approaches are urgently needed
• Applications (part of “quantum technologies 2.0”): ▫ Integrated quantum limited detection and image processing ▫ Quantum optimization ▫ Quantum simulation ▫ Quantum communication
![Page 61: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/61.jpg)
Quantum engineering for QT2.0 • Quantum UNIT engineering
▫ Qubits ▫ Couplers
DONE – engineers can take over (at least with superconducting qubits)
• Quantum STRUCTURAL engineering ▫ Multiqubit structure
design control performance characterization reliability scalability
ONLY STARTED – theory lags behind (capacity gap)
• Quantum SYSTEMS engineering ▫ Integrating different quantum and classical systems and
optimizing human interface IRRELEVANT at the moment
![Page 62: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/62.jpg)
Quantum structural engineering – the
critical challenge for QT2.0 • Accommodating incompatible requirements • Using “rule-of-thumb” estimates for
characterizing and predicting the system’s performance and reliability
• Heuristics • Scaling • “Engineering is about building reliable
structures using non-reliable components” • And now do all this for a macroscopic
quantum coherent structure!
![Page 63: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/63.jpg)
Bridging the gap
• Develop efficient methods of predicting behaviour of large quantum systems using classical means – without violating Feynman’s dictum
▫ Statistical predictions – for classes of systems, valid on average
▫ Extension of methods of quantum many-body theory and quantum statistics
▫ How exactly?
![Page 64: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/64.jpg)
For example…
• Pechukas-Yukawa (generalized Calogero-Sutherland)
Zagoskin, Savel’ev and Nori, PRL 98, 057004 (2007)
![Page 65: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/65.jpg)
• and the corresponding BBGKY chain:
Zagoskin, Savel’ev and Nori, PRL 98, 057004 (2007)
![Page 66: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/66.jpg)
Or: scaling approach
• and the use of scale models based, e.g., on
quantum metamaterials
Duke U.
UCSD
GATECH
![Page 67: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/67.jpg)
![Page 68: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/68.jpg)
Quantum metamaterials:
• Artificial optical media that have the following
properties:
▫ They are composed of quantum coherent unit
elements with engineered parameters
▫ Quantum states of these elements can be
controlled
▫ The whole structure can maintain global
quantum coherence for longer than the traversal
time of a relevant electromagnetic signal
Rakhmanov, Zagoskin, Saveliev & Nori, Phys. Rev. B 77, 144507 (2008)
![Page 69: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/69.jpg)
• A quantum metamaterial is an ideal testing bed for the development of quantum engineering and QT2.0 ▫ Simpler
▫ Promising applications Imaging
Sensing
Testing limits of quantum mechanics
▫ An AQC can be considered a special case of a (very complex) quantum metamaterial
![Page 70: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/70.jpg)
QMMs from 2008 to 2014
• Experimental prototype: Macha et al. (2013)
•Theoretical proposal:
•Rakhmanov, Zagoskin, Saveliev & Nori, Phys. Rev. B 77, 144507 (2008)
•Zagoskin, Rakhmanov, Saveliev & Nori, Phys. Stat. Solidi B 246, 955 (2009)
• Proof of principle: Astafiev, Zagoskin et al.,
Science (2010)
a
Is Is
tI0
1 m I0
(a) (b)
(d) (c)
![Page 71: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/71.jpg)
-8 -6 -4 -2 0 2 4 6 810
11
12
13
10-3
(G
Hz)
0.3000
0.3563
0.4125
0.4688
0.5250
0.5813
0.6375
0.6938
0.7500
0.8063
0.8625
0.9188
0.9750
1.031
1.088
1.144
1.200
1
0.8
0.6
0.4
b
-80 -40 0 40 800
0.2
0.4
0.6
0.8
1.0
-60
-30
0
30
60
(MHz)
t
a
Isc
Isc
tI0
1 m I0
t
arg(t)
Astafiev, Zagoskin et al., Science (2010)
f0 = 10.204 GHz
Ip = 195 nA
Proof-of-principle test
![Page 72: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/72.jpg)
a
0.0 0.2 0.4 0.6 0.8
Re (r)
0.0 0.2 0.4 0.6 0.8
-0.4
-0.2
0.0
0.2
0.4
Im (
r)
Re (r)
-122 dBm
-112 dBm
-132 dBm
Elastic scattering
![Page 73: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/73.jpg)
![Page 74: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/74.jpg)
“Ambidextrous quantum
metamaterial”
The system can be in a superposition of left- and right-handed states
![Page 75: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/75.jpg)
Initialization of a1D quantum metamaterial
Shvetsov, Satanin, Nori, Saveliev and Zagoskin (2013)
![Page 76: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/76.jpg)
Initialization of a1D quantum metamaterial
Shvetsov, Satanin, Nori, Saveliev and Zagoskin (2013)
![Page 77: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/77.jpg)
Pulse propagation through the 1D
metamaterial
![Page 78: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/78.jpg)
Lasing in a 1D quantum metamaterial
Asai et al. (2014)
![Page 79: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/79.jpg)
Asai et al. (2014)
![Page 80: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/80.jpg)
![Page 81: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/81.jpg)
Detecting a single photon’s wavefront
Zagoskin, Wilson, Everitt, Saveliev, Gulevich, Allen, Dubrovich and Il’ichev
(Scientific Reports, 2013)
![Page 82: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/82.jpg)
Model Hamiltonian
![Page 83: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/83.jpg)
Signal spectra for coherent (left) and Fock (right) input states
![Page 84: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/84.jpg)
![Page 85: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/85.jpg)
“Quantum imaging algorithms”
A. Sowa (2014)
![Page 86: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/86.jpg)
Hardware implementation:
“Quantum perceptron”
![Page 87: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/87.jpg)
Rigid quantum metamaterials
• (Saveliev and Zagoskin)
![Page 88: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/88.jpg)
Rigid quantum metamaterials
• (Saveliev and Zagoskin)
![Page 89: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/89.jpg)
On-going research
• General theory of partially quantum coherent structures
▫ Generalization of methods of quantum many-body theory
▫ Dynamic scaling theory of partially coherent structures
Collaboration: Loughborough, Cambridge, Boston, Dresden (EPSRC grant, 2015-2018)
![Page 90: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/90.jpg)
Plans
• Quantum metamaterials
▫ 2D and 3D quantum metamaterials
▫ Optical lattices-based quantum metamaterials
▫ Ambidextrous 1D and 2D quantum metamaterials
▫ Multifocal devices
▫ Quantum limited detectors (including medical applications)
▫ Quantum-classical transition research
![Page 91: Quantum engineering · qubit arrays, quantum annealers and, recently, quantum metamaterials, have witnessed significant progress over the last 15 years. This was a surprisingly quick](https://reader033.vdocument.in/reader033/viewer/2022051922/60103173ff5e811655155c7a/html5/thumbnails/91.jpg)
Conclusions • Research in quantum engineering (as applied to
quantum metamaterials, adiabatic quantum computing and related areas) has the potential for both fundamental breakthroughs and developing disruptive new technologies, new IP and business opportunities
• The research bridges quantum information science, condensed matter physics, physics of metamaterials, quantum optics, and quantum physics, and is expected to have significant impact on chemical, biological and medical research and technologies
• Quantum engineering cannot yet be separated from science and can only be developed as a part and parcel of research of macroscopic quantum coherent systems