Bulletin of the American Physical Society
52nd Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 66, Number 6
Monday–Friday, May 31–June 4 2021; Virtual; Time Zone: Central Daylight Time, USA
Session Z09: Quantum Entanglement and SensingLive
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Chair: Cindy Regal, JILA |
Friday, June 4, 2021 10:30AM - 10:42AM Live |
Z09.00001: Partitioning dysprosium's electronic spin to reveal entanglement in non-classical states Tanish S Satoor, Aurélien Fabre, Jean-Baptiste Bouhiron, Alexandre Evrard, Raphael Lopes, Sylvain Nascimbene Entanglement is one of the defining characteristics of quantum systems, while being challenging to detect and quantify. In this talk, I will present a study of the entanglement properties associated with non-classical states of dysprosium atoms' electronic spin J=8, which can be viewed as the collective spin describing a set of 2J=16 qubits symmetric upon exchange. Entanglement is often considered irrelevant here, since the qubit ensemble cannot be partitioned. In our experiments, we use optical coupling to an excited electronic state J'=J-1 to split it in two parts. The absorption of a photon corresponds to the annihilation of a qubit pair in a state defined by the light polarization. Firstly, we investigate the non-classicality of W and squeezed states, by measuring this light-spin coupling as a function of light polarization, to give direct access to the concurrence - the most common measure of pairwise entanglement. Then, we investigate the separability of the 2/14 partition by studying the mixed nature of the reduced two-qubit density matrix. For a W state and a Schrödinger cat-like state, the min-entropy of the 2-qubit subsystem exceeds the value in the initial state, thereby proving entanglement. Finally, we study the loss of qubit pairs via spontaneous emission, for states prepared in an excited level J'=J+1. We contrast W states, whose entanglement is robust to particle loss, with cat states, known to be very fragile in this regard. |
Friday, June 4, 2021 10:42AM - 10:54AM Live |
Z09.00002: Identifying and harnessing dynamical phase transitions for quantum-enhanced sensing Qingze Guan, Robert Lewis-Swan We propose the quantum Fisher information (QFI) as a tool to characterize dynamical phase transitions in closed quantum systems, which are usually defined in terms of non-analytic behaviour of a time-averaged order parameter. Employing the Lipkin-Meshkov-Glick model as an illustrative example, we predict that DPTs correlate with a divergent peak in the QFI that indicates the presence of correlations and entanglement useful for quantum metrology. We discuss a simple analytic model that connects the scaling of the QFI to the behaviour of the order parameter and propose a robust interferometric protocol that can enable DPTs to be harnessed as the basis of quantum-enhanced sensors. |
Friday, June 4, 2021 10:54AM - 11:06AM Live |
Z09.00003: Optimal Rydberg State Choice for Rydberg Atom Microwave Sensing Aurélien Chopinaud, Jonathan Pritchard Rydberg electromagnetically induced transparency offers great possibilities for the development of atom-based SI-traceable microwave (MW) sensing and communication devices. It utilizes the Autler-Townes (AT) splitting resulting from the coupling of two Rydberg states by a MW field. To create reliable and accurate devices, sources of systematic uncertainty must be carefully quantified. In particular, knowing the conditions under which the AT splitting is linear with the MW field is of great importance. In this work, using cesium atoms in a vapour cell, we investigate non-linearities originating from multi-photon couplings between neighbouring Rydberg states. By studying four different Rydberg transitions in the same frequency range we show that those couplings can break the linearity and symmetry of the observed AT splitting. We present a model which accurately predicts the behaviour of the AT splitting for any Rydberg transition accounting for multi-photon transitions. We also show that these couplings are strongly dependent on polarisation and use our model to advantageously determine the polarisation purity of the MW field. |
Friday, June 4, 2021 11:06AM - 11:18AM Live |
Z09.00004: Waveguide-Coupled Rydberg Spectrum Analyzer covering 0 to 20 GHz David H Meyer, Paul Kunz, Kevin C Cox We present a wideband RF receiver based on thermal Rydberg atoms coupled to the near field of a coplanar waveguide. We use this quantum sensor to perform spectrum analysis continuously from DC to 20 GHz with 4 MHz instantaneous bandwidth, 80 dB of linear dynamic range, and an intrinsic sensitivity of up to -120 dBm/Hz (improved to -145dBm/Hz with preamplification). Using this system as the backend of a standard rabbit-ears antenna, we directly measure ambient, real-world signals, including AM/FM radio as well as Wi-Fi and Bluetooth digital packets. We also demonstrate waveguide-readout of the thermal Rydberg ensemble via resonant, nondestructive RF probing. This work opens a path toward small, thermal ensemble Rydberg sensors that can surpass fundamental limitations to standard RF sensors and analyzers. |
Friday, June 4, 2021 11:18AM - 11:30AM Live |
Z09.00005: Atomic Vapor Cell with Integrated Electrodes for AC/DC Electric-Field Application Michael A Viray, Lu Ma, Georg A Raithel We present a glass-silicon rubidium vapor cell with built-in electrodes. The cell features eight ring electrodes that, along with the glass, form the body of the cell. The electrodes are made of conducting silicon, and they are fused to the glass parts via anodic bonding, creating a leak-proof seal. We use Rydberg-atom electromagnetically-induced transparency (EIT) and Stark effects to characterize the field created by applying a DC voltage to one of the electrodes. We also apply external microwave radiation to the cell and again use Rydberg-EIT to measure the resultant E-field strength inside the cell. The ring electrodes act as a polarizer for the microwave frequency, and we observe how the measured field is affected by microwave polarization. Given the robustness of the vapor cell, this glass-silicon anodic bonding method is a viable way of incorporating conducting surfaces into glass vapor cells, and it presents exciting opportunities for versatile cell electrode configurations in the future. |
Friday, June 4, 2021 11:30AM - 11:42AM Live |
Z09.00006: Parallel Quantum Sensing with Spatially Multimode Twin Beams of Light Mohammadjavad Dowran, Aye L Win, Umang Jain, Benjamin J Lawrie, Raphael Pooser, Alberto M Marino Quantum sensing with light takes advantage of optical quantum correlated states, such as two-mode squeezed states (twin beams) with reduced noise properties, to enhance the sensitivity of compatible measurements beyond the shot noise limit (SNL). In addition to temporal correlations, twin beams can also exhibit spatial quantum correlations that lead to localized and independently correlated spatial regions known as the coherence area. We show that the presence of multiple correlated coherence areas in twin beams can enable a parallel quantum sensing configuration. Building on our previous work on quantum enhanced plasmonic sensing~[1], we designed and fabricated a quadrant array of plasmonic sensors that we probe with one of the twin beams to simultaneously and independently detect local refractive index modulations below the SNL. With an initial level of $-5.2$~dB of squeezing, we obtain a quantum based enhancement for each plasmonic sensor of $\sim17\%$ with respect to the SNL. The degree of quantum enhancement is limited by optical losses and the finite size of the coherence area in the twin beam. The implemented parallel quantum plasmonic sensing configuration provides a proof-of-principle application for squeezed states of light with quantum correlations in multiple degrees of freedom and represents a first step towards spatially resolved quantum sensing architectures. |
Friday, June 4, 2021 11:42AM - 11:54AM Live |
Z09.00007: Unification of Metrological Powers of Nonclassical Single-Mode States Wenchao Ge, Kurt A Jacobs, M. Suhail Zubairy Nonclassical states enable metrology with precision beyond that possible with classical physics. Both for practical applications and to understand non-classicality as a resource, it is useful to know the maximum quantum advantage that can be provided by a nonclassical state when it is combined with arbitrary classical resources. This advantage has been termed the ``metrological power" of a quantum state. A key open question is whether the metrological powers for the metrology of different quantities are related, especially metrology of force (acceleration) and time (phase shifts). In this presentation, I will answer this question for all single-mode states, both for local and distributed metrology using an arbitrary linear network that achieves this maximal precision. I will show that the metrological powers for all quantities are proportional to a single property of the state, which for pure states is the quadrature variance, maximized over all quadratures. |
Friday, June 4, 2021 11:54AM - 12:06PM Live |
Z09.00008: Optimal Transmission Estimation Using Macroscopic Quantum States of Light Timothy S Woodworth, Carla Hermann-Avigliano, Kam Wai Cliff Chan, Alberto M Marino It is well known that the use of quantum resources can reduce the uncertainty in parameter estimation. Here we focus on the estimation of transmission, which is needed for a number of applications such as the calibration of a detector's quantum efficiency, ellipsometry, plasmonic sensing, measurement of absorption spectra, etc. Enhancing transmission estimation is typically done by either increasing the number of photons used to probe the system via high power classical states or using low power quantum states that give the most information per photon. We show that the bright two-mode squeezed state, a macroscopic quantum state that can be generated with a large number of photons, approaches the known minimum uncertainty in transmission estimation for any state in the limit of large levels of squeezing. Our experimental results show that we can saturate the quantum Cramér-Rao bound for transmission estimation with a bright two-mode squeezed state using an optimized intensity difference measurement and that this simple measurement is robust to extraneous losses in the experiment. Thus, we show that it is possible to use a quantum states to both probe with a large number of photons and to have more information gained per photon than a classical state. |
Friday, June 4, 2021 12:06PM - 12:18PM Live |
Z09.00009: Study on the evolution of entangled states of two four level atoms Chen Xiao-Fan In this paper, the evolution of entangled states of two four level atoms is studied. |
Friday, June 4, 2021 12:18PM - 12:30PM Live |
Z09.00010: Demonstration of a simplified protocol for dissipative entanglement of two trapped-ion qubits Daniel C Cole, Stephen D Erickson, Pan-Yu Hou, Jenny Wu, Karl Horn, Christiane Koch, Daniel H Slichter, Florentin Reiter, Dietrich Leibfried Quantum systems may be pumped into entangled states using dissipative dynamics. In this approach, dynamics are engineered that have a target entangled state as their sole attractor in the absence of experimental imperfections. Realization of these dynamics leads population to build up in the target state over time. The dissipative approach has lower sensitivity to certain errors when compared to unitary entanglement-generation protocols, and it can be used to prepare and stabilize entangled resource states in the presence of noise. We demonstrate a protocol for dissipative generation of an entangled state of two trapped 9Be+ ions. This protocol was proposed in Horn et al., NJP 20, 123010 (2018), and improves upon the one demonstrated in Lin et al., Nature 504, 415-418 (2013) by eliminating the need for sympathetic cooling. The protocol uses always-on couplings that include stimulated-Raman sideband transitions, repumping through an electronic excited state, and microwave carrier transitions to achieve steady-state entanglement. We discuss advantages of the protocol, including robustness against fluctuations in magnetic fields. We also discuss limiting errors, including heating of the ion crystal, spontaneous emission, and differential effects including magnetic field gradients and differential ac Stark shifts. |
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