Breakfast

Opening Remarks:

Jianmin Qu (Provost)

Ting Yu (Chair)

Chair: Ting Yu

Mark Saffman (Wisconsin)

Running quantum circuits on a neutral atom quantum computer

I will present results of running algorithms on a neutral atom quantum computer for preparation of multi-qubit GHZ states, phase estimation with application to a basic quantum chemistry problem, and hybrid quantum/classical optimization. The circuits use a universal set of quantum gates based on microwave and optical control of Cs atom qubits. Two-qubit gates are implemented using Rydberg interactions.

These results on a neutral atom quantum processor are the “tip of the iceberg” relative to what we believe will be possible with further development of the neutral atom approach. Atomic qubits are identical, have excellent coherence properties, and are essentially cost free with no fabrication required. Realizing the full potential of programmable large scale atomic arrays requires solving some outstanding challenges including atom loss due to imperfect vacuum conditions, optical addressing with large space-bandwidth product, high power and low noise control lasers, and crosstalk-free measurements. I will discuss these challenges and point to fruitful directions for future progress.

Luiz Davidovich (Federal University of Rio de Janeiro)

Ghost Quantum Sensing

Quantum metrology is one of the basic pillars of quantum information, together with quantum computation, quantum simulation, and quantum communication. It concerns the estimation of parameters, for which lower bounds to the precision of estimation are derived hrough a rigorous theoretical framework, established by Cramér, Rao, and Fisher for classical systems and generalized to quantum physics by Helstrom and Holevo. This framework yields simple expressions for the precision when dealing with parameter dependent unitary evolutions in closed systems. Open systems, on the other hand, require more sophisticated techniques [1-4]. This talk will demonstrate that, for open systems, a procedure analogous to quantum ghost imaging may increase the precision of estimation.

[1] B. M. Escher, R. L. de Matos Filho, and L. Davidovich, General framework for estimating the ultimate precision limit in noisy quantum-enhanced metrology, Nature Physics 7, 406 (2011).

[2] B. M. Escher, L. Davidovich, N. Zagury, and R. L. de Mato Filho, Quantum Metrological Limits via a Variational Approach, Phys. Rev. Lett. 109, 190404 (2012).

[3] C. L. Latune, B. M. Escher, R. L. de Matos Filho, and L. Davidovich, Quantum limit for the measurement of a classical force coupled to a noisy quantum-mechanical oscillator, Phys.

Rev. A 88, 042112 (2013).

[4] J. Wang, L. Davidovich, and G. S. Agarwal, Quantum sensing of open systems: Estimation of damping constants and temperature, Phys. Rev. Research 2, 033389 (2020).

* Institute for Quantum Science and Engineering, Texas A&M University, and Institute of

Physics, Federal University of Rio de Janeiro.

Work done with R. L. de Matos Filho.

Chair: Xiafeng Qian

Luis Sanchez Soto (Max Planck Institute for the Science of Light, Germany)

Random Majorana constellations

Even the most classical states are still governed by quantum theory. A fantastic array of physical systems can be described by their Majorana constellations of points on the surface of a sphere, where concentrated constellations and highly symmetric distributions correspond to the least and most quantum states, respectively. If these points are chosen randomly, how quantum will the resultant state be, on average? We explore this simple conceptual question in detail, investigating the quantum properties of the resulting random states. We find classical states to be far from the norm, even in the large-number-of-particles limit, where classical intuition often replaces quantum properties, making random Majorana constellations peculiar, intriguing, and useful. We present some experimental results that confirm the metrological power of these states.

Adrian Lupascu (IQC, Waterloo)

The demonstration of switchable coupling between a two-level system and a waveguide implemented using superconducting systems

We present our recent work on the demonstration of switchable coupling between a two-level system and a quantum field [1]. The two-level system is implemented as a superconducting flux quantum bit, with a transition frequency in the GHz range, and the field is the electromagnetic field in a superconducting waveguide. The coupling is realized based on a magnetic field controlled superconducting device. The normalized coupling strength, defined as the ratio of the qubit emission rate to the qubit frequency, ranges from effectively zero (with an experimental bound of 6 x 10^-5) to the ultrastrong coupling regime (2 x 10^-2). We performed a detailed characterization of the system using microwave scattering experiments, which allows for the extraction of the two-level system transition frequency, coupling to the field, and decoherence, relative to the system control parameters.

We discuss the prospects for using this system for future experimental investigations in quantum optics and relativistic quantum information.

1. N. Janzen, X. Dai, S. Ren, J. Shi, A. Lupascu, arXiv:2208.05571 (2022).

Sarah Mostame (IBM)

Simulating electron-phonon dynamics on IBM Quantum computers

Simulating quantum systems is believed to be one of the first applications for which quantum computers may demonstrate a useful advantage. For many problems in physics, we are interested in studying the evolution of the electron-phonon Hamiltonian, for which efficient digital quantum computing schemes exist. Yet to date, no accurate simulation of this system has been produced on real quantum hardware. In this work, we consider the absolute resource cost for gate-based quantum simulation of small electron-phonon systems as dictated by the number of Trotter steps and bosonic energy levels necessary for the convergence of dynamics. We then apply these findings to perform experiments on IBM quantum hardware for both weak and strong electron-phonon coupling. Despite significant device noise, using approximate circuit recompilation we obtain electron-phonon dynamics on current quantum computers comparable to exact diagonalization. Our results represent a significant step in utilizing near term quantum computers for simulation of quantum dynamics and highlight the novelty of approximate circuit recompilation as a tool for reducing noise

Lunch 1:00 - 2:00

Chair: Yuping Huang

Frederick H. Long (DEVCOM, Armaments Center)

Photonics and Quantum Science at DEVCOM Armaments Center

Santosh Kumar (Stevens)

A Programmable Spatiotemporal Quantum Parametric Mode Sorter

Quantum systems subtending high-dimensional (HD) Hilbert spaces have been studied due to their advantages in a higher information capacity, enhanced security, or increased resistance to noise. We experimentally demonstrate a programmable parametric mode sorter of high-dimensional quantum signals in a composite spatiotemporal Hilbert space through mode-selective quantum frequency up-conversion. By modulating the spatiotemporal profiles of the up-conversion pump, we demonstrate faithful selection of single photons in HD spatiotemporal modes and their superpositions. Our results show an improvement of the quantum mode-sorting performance by coupling the up-converted light into a single-mode fiber and/or operating the upconversion at the edge of phase matching. By optimizing pump temporal profiles only, we achieve more than 12 dB extinction for mutually unbiased basis sets of the spatiotemporal modes. This fully programmable and efficient system could serve as a viable resource for quantum communications, quantum computation, and quantum metrology.

Break 3:00 - 3:30

Chair: Rupak Chatterjee

Miguel Alonso (Institut Fresnel, France)

The geometry and topology of 3D polarization

The description of polarization for nonparaxial light is discussed, where all three electric field components are significant. Concepts like the Stokes parameters, the Poincaré sphere and the degree of polarization have nonparaxial generalizations that are not unique and/or not trivial. This talk aims to clarify these discrepancies and give a consistent framework that highlights the similarities and differences with the paraxial case, with an emphasis on geometric interpretations. Applications in microscopy and the topology of field distributions are discussed.

TUTORIAL

Adrian Lupascu (IQC, Waterloo)

Superconducting Qubits

Introduction and discussion of new research directions

Panel Discussion:

Luiz Davidovich

Igor Pikovski

Mark Saffman

Walter Strunz

DINNER 7:00 - 9:00

Breakfast

Chair: Igor Pikovski

Franco Nori

(Theoretical Quantum Physics Laboratory, Riken, Japan and University of Michigan )

Quantum Optics with Giant Atoms:

Decoherence-Free Interaction between Giant Atoms in Waveguide Quantum Electrodynamics

In quantum optics, atoms are usually approximated as point-like compared to the wavelength of the light they interact with. However, recent advances in experiments with artificial atoms built from superconducting circuits have shown that this assumption can be violated. Instead, these artificial atoms can couple to an electromagnetic field in a waveguide at multiple points, which are spaced wavelength distances apart. Such systems are called giant atoms. They have attracted increasing interest in the past few years (e.g., see the review in [1]), in particular because it turns out that the interference effects due to the multiple coupling points allow giant atoms to interact with each other through the waveguide without losing energy into the waveguide (theory in [2] and experiments in [3]).

This talk will review some of these developments. Finally, we will also show how a giant atom coupled to a waveguide with varying impedance can give rise to chiral bound states [4].

[1] A.F. Kockum, Quantum optics with giant atoms -- the first five years, https://arxiv.org/abs/1912.13012

[2] A.F. Kockum, G. Johansson, F. Nori, Decoherence-Free Interaction between Giant Atoms in Waveguide Quantum Electrodynamics, Phys. Rev. Lett. 120, 140404 (2018).

[3] B. Kannan, et al., Waveguide quantum electrodynamics with superconducting artificial giant atoms, Nature 583, pp. 775 (2020).

[4] X. Wang, T. Liu, A.F. Kockum, H.R. Li, F. Nori, Tunable Chiral Bound States with Giant Atoms, Phys. Rev. Lett. 126, 043602 (2021).

Walter Strunz (Dresden)

Open quantum system dynamics and thermodynamics from a global state point of view

Irreversible quantum (thermodynamic) processes are ubiquitous in nature and offer challenges both from an applied and fundamental point of view. Important practical (computational) and conceptual issues are still open. Fundamentally, quantum irreversibility arises as subdynamics of a unitary global evolution. In this contribution I want to stress the advantage of such a "total state" point of view and add to our understanding of open quantum dynamics, continuous measurement, and thermodynamics.

Sebastian Will (Columbia)

Assembling, Controlling and Stabilizing Dipolar NaCs Ground State Molecules

Ultracold dipolar molecules offer exciting prospects for quantum simulation and quantum computing. But creating and taming ultracold molecules is not a routine task, yet. For example, the creation of a Bose-Einstein condensate of dipolar molecules, which will be beneficial for many applications, remains an outstanding challenge.

In this talk, I will report on recent advances from our lab that have led to the creation of dipolar NaCs ground state molecules, assembled from ultracold gases of Na and Cs atoms [1,2,3]. NaCs is a bosonic molecule with a large dipole moment. The resulting interactions have long-range character, are highly controllable, and ideally suited to prepare strongly correlated and highly entangled quantum systems. Most recently, we have demonstrated strong microwave coupling between rotational states of NaCs, allowing the control of rotational qubits on a time scale of less than 10 nanoseconds, rivaling control times achieved in superconducting qubits. In addition, I will report on microwave shielding in NaCs, a technique that protects molecules from lossy inelastic collisions and dramatically increases the lifetime of our molecular ensembles. NaCs presents us with a wide range of new opportunities for quantum science.

[1] Ultracold Gases of Dipolar NaCs Ground State Molecules, I. Stevenson et al. arXiv:2206.00652 (2022)

[2] A High Phase-Space Density Gas of NaCs Feshbach Molecules, A. Lam et al., Phys. Rev. Research 4, L022019 (2022)

[3] Overlapping Bose-Einstein Condensates of Na and Cs, C. Warner et al., Phys. Rev. A 104, 033302 (2021)

Break 11:00 - 11:30

Chair: Yong Meng Sua

Xuedong Hu (SUNY Buffalo)

Adiabatic resonance for fast and robust quantum control

Author: Xinyu Zhao, Yan Xia, and Xuedong Hu

Adiabatic passage is a useful technique to realize quantum control and quantum gates. It is in general robust, albeit slow. Here we propose a universal scheme to achieve fast adiabatic passage with high-fidelity, based on the so-called “adiabatic resonance”: By designing a cyclic evolution in the adiabatic frame, the evolution path periodically returns to the adiabatic path, leading to high operation fidelity near resonance points. We first reveal the general condition of adiabatic resonance, then derive the specific condition for a two-level system, and apply it to a double quantum dot. With such a designed detuning pulse we can realize adiabatic Landau-Zener transition rapidly. Compared to other schemes aiming at accelerating the adiabatic passage, such as transition-less quantum driving, this adiabatic resonance scheme has the advantage that it does not require any additional control Hamiltonian. Lastly, we discuss the possibility of optimization and built-in robustness against noise.

We acknowledge financial support by US ARO via grant W911NF1710257, NSFC under Grant No. 11575045, the Natural Science Funds for Distinguished Young Scholar of Fujian Province under Grant No.2020J06011, Project from Fuzhou University under Grant JG202001-2.

‪Zbigniew Ficek (University of Zielona Gora, Poland)

Coherence and Anticoherence in Multi-Mode Systems

We investigate how beamsplitter- and parametric-type couplings between modes of a multi-mode system influence on coherence and anticoherence properties between the modes. The investigations are illustrated on two examples, closed loop and chain mode configurations of the modes of a tripartite optomechanical system composed of two cavity modes and a mechanical mode. In the first, the closed loop configuration, we consider the correlation properties in the transient, short time regime of the evolution, while in the second, we consider the coherence properties in the stationary long time limit. In both cases we assume that the modes are coupled to external reservoirs, which are in thermal states of unequal mean photon numbers.

We find several interesting relations between the coherence and anticoherence. Firstly, the perfect coherence is accompanied by vanishing anticoherence and vice versa, vanishing coherence is accompanied by a nonvanishing anticoherence. The modes can be perfectly mutually coherent regardless of the distribution of the population between them, the phenomenon known as induced coherence without induced emission [1,2]. However, the distribution of the population between the modes has an effect on the visibility of the interference pattern and distinguishability of the modes. Secondly, the coherence effects have a substantial effect on the population distribution between the modes, which may result in lowering the population of one of the modes. This shows that the system can be employed to cool modes to lower temperatures [3].

Thirdly, the nonvanishing anticoherence corresponds to a situation in which the modes could be entangled [4]. Thus, interference effects between modes signal the complete separability of the modes while entanglement signals the modes are mutually incoherent. Fourthly, a linear superposition of two modes interacting with thermal reservoirs of different temperatures can be perfectly coherent with the other orthogonal superposition of the modes which may result in lowering the population, cooling the third mode to lower temperatures.

In addition to coherence and anticoherence we discuss how the phenomenon of quantum steering could be distinguished experimentally by measuring the coincidence rate between two detectors adjusted to collect photons from two separate modes~[5]. We show that the coincidence rate can exhibit interference pattern in which minima signal the bipartite steering, while the maxima signal the collective steering of one of the modes by the remaining two modes.

1. X.Y. Zou, L.J. Wang, and L. Mandel, Phys. Rev. Lett. 67, 318 (1991).

2. R. Menzel, A. Heuer, and P.W. Milonni, Atoms 7, 27 (2019).

3. L.H. Sun, Y. Liu, C. Li, K.K. Zhang, W.X. Yang, and Z. Ficek, Entropy 24, 692 (2022).

4. G.S. Agarwal, Phys. Rev. A 33, 2472 (1986).

5. F.X. Sun, D. Mao, Y.T. Dai, Z. Ficek, Q.Y. He, and Q.H. Gong, New J. Phys. 19, 123039 (2017).

Bill Coish (McGill):

Non-Markovian transient spectroscopy in cavity QED

In this talk, I will describe recent work [1] where we theoretically analyze measurements of the transient field leaving a cavity as a tool for studying non-Markovian dynamics in cavity quantum electrodynamics (QED). Combined with a dynamical decoupling pulse sequence, transient spectroscopy can be used to recover spectral features that may be obscured in the stationary cavity transmission spectrum due to inhomogeneous broadening. The formalism introduced here can be leveraged to perform in situ noise spectroscopy, revealing a robust signature of quantum noise arising from non-commuting observables, a purely quantum effect.

[1] Z. McIntyre and W. A. Coish, arXiv:2206.02073

Lunch 1:00 - 2:00

Chair: Ting Yu

Tiancheng Song (Princeton)

Quantum spin Hall insulator to superconductor transition in a 2D quantum material

Two-dimensional (2D) materials and their van der Waals heterostructures provide a new platform to realize novel quantum phases in a controllable fashion. Among different kinds of 2D quantum materials, tungsten ditelluride (WTe₂) is a unique 2D semimetal, which exhibits quantum spin Hall insulator (QSHI), gate-tuned superconductivity, excitonic insulator, and ferroelectricity in a single material. In this talk, I will introduce the many faces of WTe₂ and discuss the promise of realizing Majorana physics at the intersection of superconductivity and QSHI. I will present the thermoelectric measurement technique that we recently developed, which serves as a powerful probe to study the QSHI to superconductor transition in monolayer WTe₂. Our findings highlight monolayer WTe₂ as a 2D quantum material platform for combining superconducting and topological phases in a single material.

Catherine Potts (Quantum Computing Inc.)

Image Classification with a Reservoir Photonic Computer

Reservoir computing is a machine learning paradigm designed to emulate a Recurrent Neural Network with one important distinction, the reservoir can be built using novel computational methods like photonics. Here we discuss results from applying QCi’s Reservoir Photonic Computer (RPC) to the MNIST digit classification problem. This classification problem is used as a benchmark throughout the machine learning community including the quantum machine learning world. To that end, we will also discuss how modeling the problem with the RPC is different from modeling the problem with a gate-based quantum computer.

Break 3:00 - 3:30

Chair: ‪Zbigniew Ficek

Britton Plourde (Syracuse)

Suppressing Correlated Errors in Superconducting Qubits through Phonon Downconversion

Superconducting circuits are an attractive system for forming qubits in a quantum computer because of the natural energy gap to excitations in the superconductor. However, experimentally it is observed that superconducting qubits have excitations above the superconducting ground state, known as quasiparticles, at a density that is many orders of magnitude above the expected equilibrium level. These quasiparticles are dissipative and can directly impact qubit coherence; in some cases, quasiparticle poisoning bursts can lead to correlated errors between qubits across an array, a process that is fatal to quantum error correction schemes. Quasiparticles can be generated by a range of energy-deposition sources, including energetic phonons in the device substrate produced by the impact of high-energy particles from background radioactivity or cosmic ray muons. Following an overview of these various quasiparticle poisoning mechanisms, I will describe our recent experimental work studying correlated phonon-mediated quasiparticle poisoning in multiqubit chips in the aftermath of particle impacts. I will discuss strategies for mitigating this poisoning process for future fault-tolerant quantum processors.

Chuanwei Zhang (University of Texas at Dallas)

Topological lasing and quantum sensing with non-Hermitian symmetry

Abstract: Quantum and optical technologies are emerging as two major research frontiers that could potentially revolutionize computing, communication, and sensing for modern science and engineering. One common foundation for many emerging quantum and optical technologies are the hermiticity of the underlying Hamiltonians, which govern the phases and dynamics of the physical systems. In recent years, significant theoretical and experimental progress has been made to explore symmetry (e.g., parity-time (PT)) protected non-Hermitian physics, which showcases unique properties such as exceptional points, anomalous topological states, etc. In this talk, I will discuss two applications enabled by PT-symmetry non-Hermitian dynamics in both classical and quantum optical regions: 1) topological edge mode lasing protected by a non-Hermitian bulk in the synthetic space; 2) quantum squeezing and sensing using cold atoms with anti-PT symmetry.

Ruichao (Alex) Ma (Purdue University)

Many-body entanglement in superconducting quantum circuits

Superconducting circuits, with their long coherence, strong interactions, and controllability, are ideal for exploring correlated quantum materials made of microwave photons. The precise control over coupling to engineered baths in circuits enables studies of emergent quantum phases and dynamics in both coherent and driven-dissipative settings. In recent work, we experimentally demonstrated dissipative stabilization of a photonic Mott insulator by coupling a Bose-Hubbard qubit lattice to incoherent baths. Here, I will describe our efforts toward generating novel entangled many-body states in qubit lattices in the presence of tunable baths and/or correlated dissipative dynamics. Multiple baths can also be combined to implement an effective chemical potential for photon, and provide a natural way to probe quantum transport. I will discuss our experimental progress and briefly introduce other directions we are currently pursuing.

Xuejian Wu (Rutgers-Newark)

Gravity surveys using a transportable atom interferometer

Exploiting the nature of quantum phenomena, quantum technologies are developing rapidly towards computing, communicating, and sensing. Quantum inertial sensors based on light-pulse atom interferometry are powerful tools for fundamental physics, metrology, navigation, geoscience, and civil engineering. By contrast to classical sensors, atom interferometers use photon momentum to coherently split and recombine matter waves. Since laser wavelength defines photon momentum with high precision, atom interferometers are accurate and are thus ideal inertial sensors for precision measurements. In this talk, I will present a compact and sensitive atom interferometer for measuring the absolute gravity in the field. With simplicity and sensitivity, our technology paves the way for bringing quantum gravimeters to field applications.

DINNER 7:00 - 9:00

Breakfast

Chair: Xiaofeng Qian

Girish Agarwal (Texas A&M University, USA)

Time reversed quantum metrology using squeezed states of light and matter*

It is now well appreciated that quantum physics can be used to build better sensors. Such sensors can be based on unitary systems [1,2] like interferometers or open systems based on scattering and lossy transmission channels [3-5]. The framework of the quantum Fisher information enables one to obtain best estimates of the parameters and then one can design possible experiments that can reach Cramer- Rao bounds. I would bring out not only the importance of the quantum states used as probes, but also the importance of the ‘quantum’ measurement schemes especially the ones that depend on time reversed arrangements. I would illustrate the great usefulness of squeezed states of matter and light for metrology.

[1] S. C. Burd et al., Quantum amplification of mechanical oscillator motion, Science 364, 1163 (2019).

[2] G. S. Agarwal, and L. Davidovich, Quantifying quantum-amplified metrology via Fisher information, Phys. Rev. Res. 4, L 012014 (2022).

[3] J. Wang, L. Davidovich, and G. S. Agarwal, Quantum sensing of open systems: Estimation of damping constants and temperature, Phys. Rev. Res. 2, 033389 (2020).

[4] F. Li, T. Li, M. O. Scully, and G. S. Agarwal, Quantum advantage with seeded squeezed light for absorption measurement, Phys. Rev. Applied 15, 044030 (2021).

[5] T.Li, F. Li, X. Liu, V. Yakovlev and G. S. Agarwal, Quantum-enhanced stimulated Brillouin scattering spectroscopy and imaging, OPTICA 9, 959 (2022).

______________________________________________

*work done with L. Davidovich and J. Wang

Shih-Yuin Lin (National Changhua University of Education, Taiwan)

Long baseline quantum teleportation: towards Earth-Moon distances

with Bei-Lok Hu (University of Maryland)

Quantum information experiments applying quantum optics in outer space with a very long baseline may have advantages over the current earth-bound experiments or the earth-to-satellite experiments because they can minimize the loss in light transmission and maximize the gain in time resolution. This future class of experiments, amongst them quantum teleportation and entanglement swapping, can shed light on many fundamental theoretical issues in gravitational quantum physics and relativistic quantum information. Regarding relativity theory, these experiments in an outer-space setting can involve observers at spacelike and timelike separations and explicate intriguing phenomena from different choices of time-slicing. Regarding quantum information, they may be able to ensure the causal independence of the expectation values in the Bell test. These issues are addressed in this paper with analysis and explanations.

Alex Smith (Saint Anselm)

Quantum corrections to classical time dilation

At the intersection of quantum mechanics and relativity lies the possibility for a clock to move along a superposition of two distinct classical trajectories — perhaps these trajectories correspond to different speeds or locations in a gravitational field. It is then natural to ask: what time dilation would such a quantum clock observe? Using covariant time observables described as positive operator valued measures, I will introduce a formulation of relational quantum dynamics that allows for a probabilistic formulation of relativistic time dilation and leads to an uncertainty relation between clock mass and proper time. This framework will then be used to describe quantum time dilation effects that occur when a clock moves in a superposition of different relativistic momenta and is at rest in a spatial superposition of an external gravitational field. I will argue that these quantum time dilation effects may be observable with present-day technology and offer a new test of fundamental physics in the regime where quantum coherence and relativistic effects play an important role.

Break 11:00 - 11:30

Chair: Ting Yu

Eden Figueroa (Stony Brook)

Towards the Quantum Internet: Building an entanglement-sharing quantum network across Long Island

The goal of quantum communication is to transmit quantum states between distant sites. The key aspect to achieve this goal is the generation of entangled states over long distances. Such states can then be used to faithfully transfer classical and quantum states via quantum teleportation. This is an exciting new direction which establishes the fundamentals of a new quantum internet. The big challenge, however, is that the entanglement rates generated between two distant sites decrease exponentially with the length of the connecting channel. To overcome this difficulty, the new concepts of entanglement swapping, and quantum repeater operation are needed. In this talk we will show our progress towards building a quantum network of many quantum devices capable of distributing entanglement over long distances connecting Stony Brook University and the Brookhaven National Laboratory on Long Island, New York. We will show how to produce photonic quantum entanglement in the laboratory and how to store it and distribute it by optically manipulating the properties of atomic clouds. Finally, we will discuss our recent experiments in which several quantum devices are already interconnected forming an elementary version of a quantum-enabled internet.

Songbo Xie (Rochester)

How to anticipate sudden death of tripartite entanglement?

Authors: Songbo Xie, Daniel Younis, and Joseph H. Eberly

Entanglement is not only a counter-intuitive concept in modern physics, but also a valuable resource in the most advanced technologies including quantum information science and quantum computation. However, its magic is known to be limited by the mysterious tendency for entanglement to vanish abruptly, i.e., with a discontinuous slope as a function of time, even though the entangled qubits themselves evolve steadily and analytically. The dynamical physical process associated with this mysterious tendency is commonly termed as entanglement sudden death (ESD) [Yu and Eberly, Science323, 598 (2009)].

Two-qubit ESD has been well described and multiply observed, but it remains a mystery. That is, it has not been possible to identify any initial conditions under which a state's dynamics can be confidently predicted to evolve to ESD. This challenge has been frustrated by the lack of a quantitative measure of genuine entanglement even for pure-state systems as small as three qubits. Now, with the help of a newly discovered three-qubit measure [Xie and Eberly, Phys. Rev. Lett 127, 040403 (2021)], and by bringing convex-roof construction and Legendre transforms into play, we are first able to determine the mixed-state ESD dynamics of a three-qubit system. Then, after examining various initial conditions for the system, we discover the first and potentially the only ``predictor state'' that triggers ESD.

[1] S.Xie, D.Younis, and J.H. Eberly, arXiv:2210.01854 (2022).

Lunch 1:00 - 2:00

CONTRIBUTED TALKS

Jabir Chathanathil and Svetlana Malinovskaya (Stevens)

Quantum sensing and detection using chirped stimulated Raman Spectroscopy

Vibrational coherence is the key parameter in determining the output signal strength in the four-wave mixing process of coherent anti-Stokes Raman spectroscopy. Achieving the maximum value of coherence, 0.5, is the ideal case in optimizing the backscattered signal from CARS. We derive a chirping scheme for the pulses in CARS after simplifying the four-level system into a “super-effective” two-level system based on the proposed conditions for chirping. The choice of chirp rates according to the control scheme guarantees adiabatic regime of interaction in the two-photon resonance thereby preserving the coherence at maximum value till the end of dynamics. A set of coupled Maxwell’s and Liouville-von Neumann equations for propagation of the pulses in a cloud of molecules is derived to simulate the output signal using Methanol molecule as a prototype. We demonstrate that the Maxwell’s equations are directly related to the ground state vibrational coherence and therefore the selectivity and robustness of the employed control scheme are critical in optimizing the intensity of CARS signal. Numerical analysis of the population dynamics reveals that the proposed control method is effective in preserving coherence and thereby optimizing the signal even in the presence of spontaneous decay and collisional dephasing. The pulse propagation is simulated through a distribution of molecules 1m wide and 1km away from the source. It is found that the anti-Stokes amplitude is amplified of the incident pump pulse.

Aneesh Ramaswamy and Svetlana Malinovskaya

(Stevens)

Optical Frequency Comb induced transparency in a two-level atom

The phenomenon of transparency, conventionally studied in three and higher level atomic systems, is extended to the case of an open two-level system (TLS) driven by an optical frequency comb (OFC). For open systems whose dynamics are dominated by Floquet dynamics, the time dependent response functions and absorption spectrum follows the dynamics of the transition dipoles between Floquet states. With this result, transparency in a TLS is extended to a periodic framework in which a phase-locked pulse train with harmonic phase modulation is used to control phase transport through the manifold of Floquet states. The starting part of this investigation is based on the case of transparency in closed system dynamics with chirped pulse adiabatic passage. Extension to the open system case requires control of decoherence and phase control of the system quasi-steady states, and the OFC is used to realize these goals.

We demonstrate that the two-level system can be made transparent to the resonant radiation if specific conditions for the state coherence are met. The expansion of the system space creates an increased number of pathways corresponding to an absorption process, and the phases of Floquet states can be engineered through optimizing the OFC parameters to result in destructive interference of the probability amplitude, creating reversible transparency.

Dan Younis (Rochester)

with J.H. Eberly

Virtual Detector Theory with Feynman-type Path Summation for Intense-Field Nonsequential Double Photoionization

We apply the virtual detector method, which is based on non-destructive numerical quantum detections and the propagation of Bohmian-like classical particles, to study in an ab initio way the nonsequential ionization dynamics of a model two-electron atom with helium character. Single- and double-ionization events are characterized and displayed using detector signals measured at different points in the two-electron two-dimensional position-space. Insights into different ionization and electron recollision pathways are gained from detailed virtual particle tracking and energy-time readouts. The double photoelectron momentum distribution is calculated via coherent Feynman-type path-summation over virtual particles. This study demonstrates the extension of our application of virtual detector theory to strong-field multi-electron quantum dynamics.

David Luo (Stevens)

Geometric phase and geometric decoherence in quantum open systems

The geometric phase has been used in various fields of study, and has been extended to non-adiabatic, non-cyclic and non-Hermitian systems. In this talk, we go over our results using the geometric phase to study the properties of non-Markovian open system dynamics, using a stochastic quantum trajectories approach. A remarkable feature of the open system’s geometric phase obtained from our theoretical formulation is that the geometric phase can be obtained regardless of the existence of the master equations, while the environmental noise features such as memory effects are fully accounted for. We demonstrate that the geometric phases for a general open quantum system can be fundamentally modified by its non-Markovian environments. We also investigated the geometric nature of decoherence by defining a complex-valued geometric phase through stochastic pure states describing nonunitary, noncyclic, and nonadiabatic evolutions. The ensemble average of the complex geometric phases for the pure stochastic states yields a conventional geometric phase together with an amplitude factor. We show that the decoherence process described by the decaying amplitude can be a geometric quantity independent of the system’s dynamics. In addition, by using a structured bath, we can probe the intricate relationships between the non-Markovian effects and the geometric phase, where it is found a divergence of the geometric decoherence may serve as a sufficient condition for non-Markovian dynamics.

Break 3:00 - 3:30

Shenyu Zhu (Stevens)

Non-line-of-sight Sensing and Imaging Using Nonlinear Optical Gating

Abdelali Sajia (Stevens)

Realizing Credible Optical Superresolution via Entangled Partner

Zhaotong Li (Stevens)

Phase Transitions in a Nonlinear Optical Ising Machine

DINNER 5:00 - 7:00