summary of proposal · web viewvia stark and/or zeeman shift [fig. 1(b)]. as a result, after the...

LABORATORY DIRECTED RESEARCH AND DEVELOPMENT

PRELIMINARY PROPOSAL (FY2021 FUNDS)

TITLE: QUANTUM ENHANCED TRACKER TOPIC: QUANTUM INFORMATION SCIENCE, QUANTUM SENSING DEVICES

LEAD INVESTIGATOR SHUKUI ZHANG

Phone: 757 269 5575

Email: [email protected]

Date: 5/30/2020

Department/Division: Accelerator/JLAB, and Physics/ W&M

Other Personnel: Seth Aubin (W&M), Todd Averett (W&M)Eugeniy Mikhailov (W&M), Irina Novikova (W&M)

Proposal Term: From: 10/2020Through: 09/2021 If continuation, indicate year (2nd/3rd):

Division Budget Analyst Kelly WebsterPhone: (757) 269-7575Email: [email protected]

This document and the material and data contained herein were developed under the sponsorship of the United States Government. Neither the United States nor the Department of Energy, nor the Thomas Jefferson National Accelerator Facility, nor their employees, makes any warranty, express or implied, or assumes any liability or responsibility for accuracy, completeness or usefulness of any information, apparatus, product or process disclosed, or represents that its use will not infringe privately owned rights. Mention of any product, its manufacturer, or suppliers shall not, nor it is intended to imply approval, disapproval, or fitness for any particular use. A royalty-free, non-exclusive right to use and disseminate same for any purpose whatsoever, is expressly reserved to the United States and the Thomas Jefferson National Accelerator Facility.

2 of 21 JLab LDRD Proposal

THOMAS JEFFERSON NATIONAL ACCELERATOR FACILITY

Abstract

From the lowest energy atomic processes, through radioactive decay, particle production in nuclear and high-energy research, to the detection of the highest energy cosmic rays, charged particle tracking is one of the most widely used detection techniques. The goal of this proposed project is to develop a “quantum tracker” capable of providing 3D images of charged particle tracks across a wide range of energies, taking advantage of the Quantum Information Science in quantum control of light and matter. As a particle passes through the quantum tracker, it perturbs the quantum wave functions of atoms in a dilute alkali vapor. Since the atoms in a modified quantum state interact with light differently, it becomes possible to visualize the particle track by observing in what region of space the light absorption or polarization has been affected by the moving electron. This novel method has the potential for much finer resolution and higher sensitivity with better signal-to-noise compared to typical gaseous or scintillator-based methods. By optical detection of tracks in three dimensions on remote CCD cameras, this system aims to simplify tracking commonly achieved using cumbersome multi-channel, multi-plane detectors. For the first proof-of-principle experiment, we will demonstrate the capability of the quantum tracker by imaging low energy electrons easily produced using a compact commercial electron source. Guided by this initial R&D a prototype detector could be tested using relativistic electrons from Jefferson Lab (JLab) electron sources and eventually in one of the experimental halls. Simultaneously, we will conduct theoretical and numerical studies aimed at optimizing performance for larger scale particle detection at facilities such as JLab and the EIC. This proposal combines the multi-disciplinary expertise in nuclear physics, accelerators, quantum optics, and atomic physics from researchers at JLab and the College of William and Mary (W&M).



Summary of ProposalDescription of Project

Experimental nuclear and high-energy physics research requires particle identification and accurate reconstruction of particle tracks. At the Thomas Jefferson National Accelerator Facility (Jefferson Lab, or JLab), electrons are scattered from a wide variety of fixed targets. In some reactions, one looks for single particles in small acceptance, high resolution spectrometers such as those in experimental Halls A and C. In Halls B and D, one needs to reconstruct several tracks from one event to look for e.g. rare meson production. The high luminosity available at JLab in particular tends to make the track reconstruction difficult and costly due to the large number of channels required to handle the detector rates. Any improvement in rate capability, cost or size of the tracking device may greatly benefit current and future experiments.We propose to develop a radically new particle detector, a “quantum tracker” for 3D imaging of charged particle tracks. The proposed detector will rely on, and benefit from, the extremely high sensitivity of atoms, prepared in a specific quantum superposition, to external perturbations. We will prepare atoms in a so-called “dark superposition”, which inhibits any fluorescence. A passing charged particle will disturb this quantum state, allowing atoms to absorb probe light and fluoresce, thus enabling direct imaging of the particle trajectory with high resolution. This method has similarities with Cherenkov detectors where a charged particle produces light along its track, but with the major advantages of increased sensitivity due to the low energy required to perturb the engineered quantum state, the ability to amplify the signal using a drive laser passing through the medium, and the ability to provide a 3D track.

Expected Results (Year 1)We expect to provide following deliverables at the end of the 1st year:Proof-of-principle tracker demonstration: We will produce a table-top system to image a continuous beam from a compact electron source using 2D or 3D imaging of the polarization rotation and/or absorption in a rubidium vapor.Optimization strategies for reaching single-particle sensitivity: We will complete evaluation on the tracker performance for various parameters of the electron source. We will also evaluate optical interrogation techniques to develop a strategy for optimizing performance.Theoretical and numerical model for the atom-light quantum state interaction with relativistic electrons: We will identify the optimal



quantum superpositions and the expected tracker performance for relativistic electrons.Working detector design: We will use the information gained from the first-year R&D and simulations and complete a design for a quantum tracker intended for testing in an experimental hall at JLab.

The proposed research in this proposal perfectly matches the special interests outlined in the JLab’s LDRD funding topics and the recent DOE’s call for promoting QIS Research and Innovation for Nuclear Science, could lead to unprecedented impact in nuclear physics study and significantly boost JLab’s research capability and standing in this emerging field.



Proposal NarrativePurpose/Goals

In modern nuclear and high energy physics research, large-scale detectors are used to identify the particles produced in scattering experiments and to precisely determine their kinematics. Smaller scale detectors are used as beam position and profile monitors. A charged particle’s momentum and scattering angle are typically measured using an array of tracking detectors located after a series of dispersive and focusing magnets. The most common detectors for this purpose are based on measuring small signals produced by ionization of a gas in an array of closely spaced conductors as the particles pass through. Generally speaking, the quality of the detector is dictated by its maximum particle detection rate, which is related to the ability to operate in a high background environment and, its spatial resolution for reconstructing particle tracks. We propose a radically new scheme for charged particle detection where precise 3D optical images of tracks can be produced by perturbation of the quantum wave function of a dilute alkali vapor as particles pass through. The proposed detector has the following advantages over traditional ionization detectors: a) it will be a single container with no internal detector elements, high voltage, or gas for ionization, b) due to operation at very specific optical wavelengths, it will be insensitive to all other optical photons and so does not need to be light-tight, c) it will be insensitive to neutral particle backgrounds, d) because the detector signal is recorded optically, the spatial resolution will be limited only by the precision of the optical system and with no need for high-speed electronic readout and storage of hundreds of detector channels, and e) a quantum tracker will replace the multiple layers of traditional detectors needed to reconstruct a track in 3D. The freedom from the limitations and overhead associated with using multiple ionization-based detectors with hundreds of channels will have a far-reaching impact on many areas of modern physics research requiring charged particle detection. One can imagine replacing multi-plane wire chambers or GEM detectors in single particle spectrometers like the HRS, SHMS or Super BigBite with a single quantum tracking chamber. Replacing large volume wire chambers in e.g. CLAS with quantum trackers compatible with the toroidal geometry but having much simpler readout and DAQ, could likely improve the low rate limit common to these detectors.


Figure 1: (a) An electron travels (red dashed line) through a gas of rubidium atoms (87Rb), which experience the electric and magnetic field of the passing electron. The variable d represents the impact parameter of the electron with a given atom. (b) Representation of the energy shift E experienced by an atom due to the field (electric or magnetic) of the electron. In this simplified model, the |c state experiences an energy shift from the external field of the electron, while the |b state remains unshifted.

(a) (b)


Approach/Methods1. Basic operational principle

The proposed quantum tracker can be thought as a quantum analog of a cloud chamber, where instead of a physical trace, a charged particle will imprint its track on the quantum phase of the atomic quantum wave-functions, which will be then imaged with high speed and resolution. The key advantage of such an approach is its super low exchange energy between a passing particle and the quantum atomic medium, and negligible ionization rate. One can even possibly think about it as a quantum non-destructive detection, where only the phase of the coherence is perturbed by a passing particle.

The heart of the

detector is a dilute gas of Rb atoms prepared in a special quantum superposition of atomic energy levels, e.g., ¿Ψ ini ⟩=

1√2

(¿ b ⟩−¿ c ⟩ ). If a rapidly moving electron passes in the vicinity of such an atom [Fig. 1(a)], then its electric and magnetic field will momentarily shift the atomic energy levels by ΔE(t) via Stark and/or Zeeman shift [Fig. 1(b)]. As a result, after the electron has passed and the atom returns to its original state (i.e. elastic interaction), the information about the passed particle will be retained by the relative phase of its quantum state:

(t)=(1/ℏ)∫𝑝𝑢𝑙𝑠𝑒 Δ𝐸(𝑡′)𝑑𝑡′, Only atoms close to the electron’s trajectory will acquire this extra phase and will end up in a modified quantum state ¿Ψ fin ⟩= 1

√2(¿b ⟩−ei Δ ϕ∨c ⟩ ). Modern

quantum control techniques of light-atom interactions now allow us to


Figure 2: Schematic of the proposed quantum tracker. The atoms, contained in a rectangular glass cell, are prepared in the dark state using laser beams. The filters installed after the cell remove read out laser light, allowing only the light scattered by atoms in perturbed quantum state through. This light trace of the charge particle is then recorded using an imaging lens system and a camera (not shown). Two-dimensional illumination will enable 3D reconstruction of the original particle track.


measure this relative phase φ with high precision via optical measurements of resonant light absorption, fluorescence and polarization rotation [1,2]. If we image the accumulated phase φ for each atom in the gas (i.e. via phase-sensitive optical measurements), then the change in optical atomic susceptibility near the electron will reveal its trajectory through the spatially dependent phase. 2. Proof-of-principle experiment arrangement The choice of the participating atomic states |b⟩ and |c⟩ determines the atomic sensitivity to either the electric field or the magnetic field [3]. For the proposed initial experiment we will focus on tracking the electron via its magnetic signature, i.e. by monitoring the shift in atomic magnetic sublevels due to the magnetic field of the moving electrons. For the 87Rb atoms (which we are planning on using for the experiments) we will focus on the atomic ground levels (5S1/2) that exhibit strong magnetic field energy shift due to the Zeeman effect ΔEZeeman=μB|B|, where |B| is the value of the

magnetic field, and μB =1.4 MHz/Gauss. We can estimate that for an impact

parameter d=1μm, the expected phase accumulation due to the Zeeman

effect is quite weak at Δφ=2.8×10-9 radians per electron. That small effect is why for the initial tests we will use a high-current electron source to generate a larger signal: for a phase accumulation time of 1 ms, a 60 nA electron beam is expected to generate a 1 radians phase variation, easily detectable optically [1,2].

The proposed arrangement of the quantum particle tracker is shown in Fig. 2. A test volume will be filled with a relatively low density (around

1012 cm-3) atoms prepared in a desired quantum superposition of the ground-state magnetic sublevels. Once a charged particle passes through the medium, its magnetic fields will change the phase of the atomic quantum state, which then can be detected through an optical signal (fluorescence and/or absorption imaging) [4]. This optical signal will be imaged with a set of cameras looking at the beam in two projections, which will allow 3D reconstruction of the particle path. Such a measurement can be performed quickly, with a range of


Figure 3: A conceptual experiment layout. The electron beam from E-gun is deflected and coaxially propagates with laser beam through Rb vapor chamber before deflected to a Farady-cup. Fluorescence and absorption/polarization are detected by CCD cameras. A: collimating aperture, RVE: Rb vapor enclosure, ESD: electrostatic deflector. Some equipment such as Rb source, vacuum pumps, optical and e-beam collimating elements are not shown.


time scales from a few nanoseconds to milliseconds. Once the track information is recorded, the atoms can be quickly reset to the unperturbed quantum state using one or two laser pulses.

We can further enhance the measurement precision by using specially prepared quantum light to image the electron track. For example, when the phase variation results in the optical polarization rotation, a polarization-squeezed optical probe can be used for imaging to further improve signal-to-noise beyond the classical limits [5]. Another possible quantum enhancement can come from applying quantum twin intensity-correlated optical fields that allow compensation for many technical noises and intensity fluctuations [6,7]. Finally, a proper phase optimization of the atoms can allow for super-resolution imaging of a track.

3. Basic experimental setupIn the initial proof-of-principle experiments we will use a specially-

designed reconfigurable vapor cell that can be connected to a vacuum system directly connected to an electron source, a commercially available compact electron gun (up to 10keV, 1nA ~ 100uA current) with robust control and beam collimation for user-friendly operation. This system will provide us with the flexibility necessary to identify the optimal operation conditions for electron tracking. This design, shown in Fig. 3, will have an open channel for a collimated e-beam to enter and exit the cell volume, and optical-quality windows on four perpendicular walls for laser access. We will explore the option of using spectroscopic heat pipes [8] in which the cell containing the Rb vapor will be placed in an additional enclosure filled with inert gas to help confine the atoms inside the inner volume even in the presence of openings on the two opposite ends of the enclosures. Such systems have been successfully used for X-ray absorption spectrometry [9].

Since the AMO


Figure 4: (a,c) The schematic of the mock quantum tracker arrangement, in which the role of the electron beam is played by another laser beam, propagating parallel (a) or perpendicular to the imaging beam. (b,d) the experimental observation of the test beam imprint due to the polarization rotation of the imaging beam. Depending on the test beam orientation, we observe either the test beam cross-section, or its longitudinal “shadow.”


group at W&M has significant expertise and experimental capabilities for measuring the phase evolution of atomic spin quantum wave-functions in magnetic field, we will start by measuring the magnetic field created by a continuous electron beam in the 50 nA - 1 µA range. In the beginning, we will illuminate the atoms with linearly polarized resonant light, thus preparing atoms in a particular superposition of the Zeeman magnetic sub-levels. The magnetic field of the electron beam and the induced phase change will cause phase evolution of this state that will manifest itself through the rotation of polarization of the transmitted optical field. This effect, known as nonlinear magneto-optical rotation (NMOR) [10], is widely used for precision magnetic field measurements, and will provide a first straightforward demonstration of particle tracking using quantum states of atoms. The polarization rotation angle will be proportional to the electron flux, as well as to the atomic parameters, such as atomic density, laser power and detuning, etc., and thus will be used to optimize the detection sensitivity.

This setup will also allow for a first demonstration of electron beam imaging. Since only the atoms in the vicinity of the electron beam will be affected by its magnetic field, its location and longitudinal cross-section can be recorded by imaging the perpendicular polarization component of light by placing a polarizer that rejects the original laser polarization. If conducted in two perpendicular directions, these images will allow 3D reconstruction of the beam. We will also use this first-stage prototype setup to optimize the resolution of the detection system. To illustrate the imaging

possibility, we used a mock-up experiment, shown in Fig. 4(a,c), where the perturbation caused by the electron beam is mimicked by another laser beam. One can clearly see in Fig.4(b,d) that the spatial information about the beam is easily detected, while the rest of the imaging beam is effectively diverted. Coordinated illumination of the interaction region from three directions would allow, in principle, a 3D reconstruction of the beam path.The next step toward detecting single particle tracks will be done using pulsed detection, in which



the preparation and the readout of the atomic quantum state are separated in time. For these measurements, we will use the quantum memory techniques developed by Novikova’s group [2, 10, 11]. As for the CW case, we will explore both magnetic and electric field sensitivity, using a pulsed electron source (It is possible to run the e-gun with a pulse width ranging from 2 μs to DC, 500 ns rise/ fall time, and rep rates up to 5 kHz, using an optional power supply). The measurement procedure will include three main steps:

1. Detector initialization: A strong laser pulse (mono- or bi-chromatic) will be applied to optically pump all atoms into the desired quantum superposition.2. Track recording: The laser light is turned off, allowing atomic superposition to evolve in response to passing electrons. 3. Optical readout: The local changes in the atomic quantum states are recorded using a specially configured read-out laser pulse, which is designed not to interact with the atoms in the unaltered quantum state, but to produce strong directional light emission or fluorescence if the superposition of the atomic quantum state has been altered. Imaging the areas corresponding to such emission will allow for particle track reconstruction.

4. Theoretical optimization of detection for relativistic particle detectionAnother important objective of the proposed research program is the better-informed design of the quantum tracker for relativistic particles that will be based on both incoming experimental results and theoretical modelling. During FY2021 the particular focus of the theoretical work will be on identification of the optimal atomic quantum superposition(s) and optical interrogation methods. While the experimental effort will focus on detection of electrons’ magnetic field effect on quantum superpositions of atomic ground states (due to its relative simplicity and availability of equipment), we will also conduct the calculations for evaluating the prospects of using highly excited atomic Rydberg states (e.g. with principal quantum number n ≥ 50). We may be able to take advantage of the strong electric field sensitivity of such states [13] , since an electron travelling at a relativistic velocity v (e.g. at 1 GeV) generates an electric field that is amplified by a factor of γ=1 /√1−(v /c)2 in the transverse direction. If the orbital atomic angular momentum is kept small, then the electric field dependence is quadratic: ΔEStark =-½⍺|E|2, where |E| is the magnitude of the electric field,

and α is the polarizability. For example, for the |c⟩=|50P3/2⟩ the polarizability is ⍺=2.14×10-29 C·m2/V, about 10 orders magnitude more than the 5S1/2 ground levels [14]. At low energies, the Stark effect in Rydberg atoms is expected to enable single particle detection. At GeV-scale energies the calculations



are more difficult. A naive estimate for sensing via the quadratic Stark shift (for a n=50 P3/2 Rydberg atom) indicates the potential for a large radian-scale signal for a single electron, despite the atto-second phase accumulation time.

Goals for FY2021· Quarter 1 (October 2020 - January 2021)

a. Identify and secure essential equipment, lab space and a graduate student. Complete system design. Purchase parts and the electron source. Complete a work ES&H safety review.

b. Assembly of the vacuum setup, tests and characterization of the electron gun (Zhang, Averett, Aubin).

c. Construction and tests of the Rb cell, integration of the Rb vapor cell and optical input/outputs into the vacuum system (Zhang, Averett, Aubin, Mikhailov)

d. Initial optical detection of high-current electron beam (Novikova, Mikhailov, Aubin, Averett) (b, c, and d may be continued in Quarter 2 in case of any delay)

Quarter 2 (January 2021 - April 2021)e. Continue to finish the work (b, c, d) in Quarter 1 if necessary.f. Evaluation of the sensitivity of various optical detection methods,

i.e. fluorescence, absorption, polarization rotation (Novikova, Mikhailov, Aubin, Averett)

g. Optimization of high-current electron beam imaging (Zhang, Averett, Aubin, Mikhailov, Novikova)

Quarter 3 (April 2021 - July 2021)h. Evaluation of the quantum tracker sensitivity for a low-current

electron beam and single electrons (Zhang, Averett, Aubin, Mikhailov, Novikova)

i. Modifications and improvements of the quantum tracker design, based on the acquired experimental information (Zhang, Averett, Aubin)

j. Theoretical development of further sensitivity enhancement for relativistic electrons using electric field imaging (Zhang, Averett, Aubin, Novikova, Mikhailov) and quantum imaging techniques (Novikova, Mikhailov, Aubin).

Quarter 4 (July 2021 -October 2021)



k. Demonstration of 3D imaging capability for high- and potentially low-current electron beams.

l. Further theoretical development of the quantum tracker sensitivity enhancement for relativistic electrons, based on improved experimental apparatus (Zhang, Averett, Aubin), electric field imaging (Zhang, Averett, Aubin, Mikhailov, Novikova), and quantum imaging techniques (Novikova, Mikhailov, Aubin).

m. Evaluation of our results to motivate the design of a prototype detector for testing in an experimental hall at Jefferson Lab

n. Preparation of a report of the experimental results for publication in peer-review journals (Zhang, Averett, Aubin, Mikhailov, Novikova).

Required Resources (Year 1)This proposed project relies heavily on available resources from both JLab and W&M.

We expect to need the following resources from JLab (in Year 1): Lab space, test bench for vacuum work and electron gun

testing, including vacuum pumps, vacuum diagnostic equipment, computer and control software

Generic software for optical design and electron beam simulations

Optical table, opto-mechanical parts, optics, imaging cameras, lasers, and optical/laser diagnostics (power detector/meters, spectrometers, beam profiler, etc) software and essential electronics (signal generators, oscilloscopes, etc)

Machine-shop for fabrication or refurbish of non-purchasable parts

The proposed research program will also take full advantage of available resources for atomic state quantum control, optical state preparation, manipulation and analysis, as well as nonlinear and quantum light-atom interactions, developed by the AMO groups (Aubin, Novikova, Mikhailov) and experimental nuclear group (Averett). The experimental equipment and capability, available at the WM campus, will provide a lot of flexibility in the initial experiments and will allow easy re-configurability critical to identifying the most successful strategy for optical particle detection and track imaging. Below is the list of equipment, available for sharing:



Experimental Nuclear Physics and Polarized 3 He Target Laboratories, Averett, William and MaryEquipment available for project:

● High-vacuum system for filling of glass cells with alkali metals and noble gases

● NMR and EPR systems● VME and NIM electronics● RF electronics and coil systems ● Scintillators and photomultiplier tubes ● High voltage supplies

Bose-Einstein Condensates Lab, Aubin, William and MaryEquipment available for project:

● 2x optics workstations (3ft x 5ft, mobile)● 1.5 W Titanium-Sapphire laser: Coherent MBR-110 + 10 W Verdi

(shared with Prof. I. Novikova).● CCD camera (PointGrey/FLIR, industrial grade, triggerable) to be

shared with project. Aubin Lab custom imaging software can be used with this camera.

● Power supplies: 150 A, 15 A, 10 A, 3 kV & 10 kV high voltage sources.● Electronics equipment: 20 GHz spectrum analyzer and vector network

analyzer, 1 GHz oscilloscope. The Aubin group has expertise in the design and construction of analog, high current, digital, photon counting, and RF systems.

Quantum Optics Laboratory, Novikova and Mikhailov, William and MaryEquipment available for project:

● Laser systems for Rb atom quantum control : Toptica DL, external cavity diode laser (795mn); New Focus external cavity Vortex laser (795 nm), Toptica TA amplified laser system (795 nm)

● Microwave electronics : Agilent microwave frequency synthesizer E8257D (0-20 GHz), Agilent spectrum analyzer E4405B (10 kHz - 13.2 GHz)

● Detectors : 4 Perkin-Elmer avalanche photodetectors, fast amplified photodiode (up to 8GHz).

● Imaging equipment: Meadowlark spatial light modulator, Princeton Instruments Pixis 400BR-X Camera.

Anticipated Outcomes/ResultsThe main focus for Year 1 (FY2021) will be the proof-of-principle for the quantum tracker concept by producing a benchtop system based on optical detection of low energy electrons in a room temperature rubidium vapor (T < 100° C). A low energy CW electron source and vacuum system will be



used for the first stages. The integration of the atomic, optical, and electron source components will be accomplished jointly by JLab and W&M.

Initial work will use a 10-100 µA electron beam to obtain a first imaging signal by laser interrogation of the magnetic (Zeeman) disturbance in the rubidium vapor due to the passing electrons. Once the imaging process has been optimized, the beam current will be reduced to the 0.1 nA range or lower to determine the detection limit.

Another objective of the project will be the theoretical modeling and design development for capabilities of rapid imaging of single particle tracks (electrons or other). Below we outline some additional scientific and technical areas we expect our first-year research to address.

Detection speed capabilitiesMulti-photon all-optical quantum state manipulations allow one to prepare and read-out target atomic states at a rate limited only by the strength of the optical fields, and thus are not limited by natural relaxation times of the system. Recent experiments demonstrate the possibility of creating and then reading-out the quantum spin state in a Cs vapor cell at a rate approaching 1 GHz [15]. Similar detection rates can be achieved in the proposed quantum tracker, as the signal light pulse will be produced in response to the quantum state disturbance from a passing particle. However, operation at such a high rate will require the development of a custom laser system that can provide sufficient optical power and proper pulse duration. For the year 1 proof-of-principle prototype, we will use off-the-shelf laser systems, which will limit the detection to sub-MHz rates.Track reconstruction capabilitiesThe track recording is performed at the same rate as the probe pulse read-out. The spatial information for each particle’s trajectory will be extracted from images of the bright track where the quantum atomic state has been perturbed (illuminated by the probe laser). The most straightforward way to record these tracks then is by using fast CCD cameras, as they are sensitive to the near-infrared and visible light of the experiment, have low background noise, and have high spatial resolution. The best commercially available cameras are currently capable of frame rates > 20 MHz [16]. For the year 1 prototype, we will use CCD cameras with frame rates in the 10-100 Hz range.

Spatial resolution capabilitiesThe spatial resolution of the track reconstruction will ultimately be limited by the optical resolution of the imaging system, which can approach the wavelength of the readout laser (400 - 800 nm). In the proof-of-principle prototype, we may need to sacrifice the detection resolution and collect



light from a larger area to boost the optical signal during the optimization stage.

Particle sorting capabilitiesTheoretical estimates show that the relativistic enhancement of the electric field created by a passing charged particle will result in a strong dependence of the phase shift induced in the atoms via the Stark effect on the relativistic gamma parameter 𝛾. This dependence, therefore, will translate into distinct transverse spatial patterns in the phase of quantum atomic states imprinted by the particle track. Since relativistic particles of similar energy but different masses have significantly different gamma values, the analysis of the transverse phase patterns can be used for particle identification.

Detection volumeThe proof-of-principle benchtop system in year 1 will use a stainless steel vacuum system (with differential pumping) to house the rubidium vapor with a detection volume of a few cubic inches. This system will help guide the design of a second generation system where the vapor would be held in a glass container or cell for easy optical access. The detector could consist of one large cell or an array of smaller cells. The addition of an inert gas can be used to reduce the pressure differential between atmosphere and the cell interior. Similar or more advanced techniques have been employed at many labs including JLab for experiments involving gas targets [17].

Investigation of requirements for a full-scale detectorThe detector volume will be mostly filled with a dilute (<1013 atoms/cm3)

atomic gas, resulting in an extremely low rate of direct ionization along the particle track and minimal energy exchange with the detecting medium (energy loss ≤ 1 eV/m, Bethe formula). A full-scale detector would require the use of thin window material and external laser and camera systems so as not to interfere with the passing particles. Our benchtop system based on a modular vacuum system that allows us to test a variety of laser, optics and camera configurations. The effect of the Rb vapor on the system components and possible window and cell designs can also be tested.

Operation in the presence of strong external fieldsStrong magnetic and/or electric fields will modify the energies of the atomic levels and thus the frequencies of the atomic transitions. In principle, these fields should not reduce the detection capabilities of the tracker, and can be compensated for by adjusting the laser frequencies and (if necessary) polarizations. However, strong inhomogeneities in these fields may deteriorate the quality of the prepared quantum state, leading to reduced performance. Mitigation techniques will be investigated, including the



accommodation of field gradients for NMR-type imaging. Effects of external fields can be tested on the benchtop system.

Future directionBased on a successful R&D in year one, we anticipate continuing this project for two additional years. At the end of the first year, we will first have a proof-of-principle demonstration of the concept and a working benchtop tracking device. We will have cross-checked our computations for the sensitivity of the method. In the second year we will focus on optimization of the system for detecting and accurately reconstructing single particle tracks. By the end of the second year we will have designed and begun construction of a modest-sized prototype detector for in situ tests in one of the JLab experimental halls. In the third year we will begin in situ tests at JLab with the aim to have all of the knowledge and information necessary to build a full-scale detector that could be used in future experiments.

Accomplishments in Previous YearsN/A

Budget ExplanationPersonnel (Year1):

Shukui Zhang (JLab, 3 months/25%) – PI, manage and make plan for project tasks and routine work. Communicate with team members and organize regular meetings. Co-supervise a graduate student with other W&M faculty and participate in all major activities, in particular in electron beam and optical systems. Seth Aubin (W&M, 1 month) – co-PI, co-manage the construction of hardware including vacuum system, Rb enclosure, laser and optics, participate in quantum light-atom interaction measurements, contribute to theoretical calculation. Co-supervise a graduate student with other W&M faculty and participate in all major activities.Todd Averett (W&M, 1 month) – co-PI, co-manage the construction of hardware including vacuum system, electron source, laser and optics, provide expertise for nuclear physics detector requirements. Co-supervise a graduate student with other W&M faculty and participate in all major activities.Eugeniy Mikhailov (W&M, 1 month) – co-PI, co-manage the work on the optical interrogation and detection, participate in activities related to interfacing of vacuum equipment, an electron



source, and an optical system; work on data acquisition and post-processing. Co-supervise a graduate student with other W&M faculty and participate in all major activities.Irina Novikova (W&M, 1 month) – co-PI, identify and optimize the quantum light-atom interaction for optical detection, co-design optical imaging setup, contribute to theoretical calculation. Co-supervise a graduate student with other W&M faculty and participate in all major activities.Graduate student (100%) – Participate in all activities, in particular electron beam simulations, vacuum and optical setup/testing.

PIs: $107.6kGraduate Student $28.5k Total labor cost: $136.1k

Travel:Year 1: no travel

Purchases/procurements:Commercial electron source: $25kVacuum system (for electron source operation): $18kD2 laser (100 mW) (drive laser): $30kOptical hardware supplies (fibers, polarizers): $28kElectro-Optic Modulator & Acousto-Optic Modulators: $10kElectronics : $10kWavemeter: $15kComputer: $2kMachine-shop $3k

Total equipment and supplies: $141k

Total cost with overhead: $338.82k



References

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