Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session T39: Quantum Metrology and Sensing IVFocus Recordings Available
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Sponsoring Units: DQI Chair: Yeghishe Tsaturyan, UChicago Room: McCormick Place W-196A |
Thursday, March 17, 2022 11:30AM - 12:06PM |
T39.00001: Multimode optomechanics to reach and evade displacement sensitivity limits Invited Speaker: Laure Mercier de Lepinay The measurement of mechanical oscillators' displacement is at the basis of many fundamental physics experiments. Fundamental sensitivity limits, where the measurement process becomes the dominant source of measured fluctuations, can nowadays be reached. Optomechanics has recently explored a path to reach and surpass these limits: coupling the displacement to contingent degrees of freedom, and redistribute fluctuations towards these rather than the observable of interest. This idea first emerged with the two motional quadratures of a mechanical oscillator, limiting the quantity of interest to one quadrature only. More recently, optomechanical systems involving multiple modes have extended this concept beyond the measurement of a single motional quadrature. |
Thursday, March 17, 2022 12:06PM - 12:18PM |
T39.00002: Entanglement-enhanced optomechanical sensing Yi Xia, Aman Agrawal, Christian M Pluchar, Kewen Xiao, Quntao Zhuang, Dalziel J Wilson, Zheshen Zhang Optomechanical sensors allow ultrasensitive measurements of force, acceleration, and magnetic fields. Nonclassical resources such as the squeezed light have been harnessed to boost the performance of individual optomechanical sensors. Joint measurements undertaken with multiple optomechanical sensors would further improve sensitivity; however, a pathway toward quantum enhancement in this multi-sensor regime has not been explored. In this work, we propose and experimentally demonstrate that entangled light can improve the sensitivity and bandwidth of an optomechanical sensor array. Specifically, we prepare entangled optical probes to jointly read out the displacements of two mechanical membranes. We observe entanglement-enhanced sensitivities at the shot-noise-dominated frequencies and increased bandwidth over thermal-noise-dominated frequencies, subject to a sensitivity-bandwidth tradeoff. Our work opens a new avenue for ultraprecise measurements with an array of quantum-enhanced sensors with applications ranging from inertial navigation and acoustic imaging, to searches for new physics. |
Thursday, March 17, 2022 12:18PM - 12:30PM |
T39.00003: Demonstration of quantum-optimum entanglement-enhanced covert sensing Zheshen Zhang, Shuhong Hao, Haowei Shi, Christos Gagatsos, Mayank Mishra, Boulat Bash, Ivan Djordjevic, Saikat Guha, Quntao Zhuang The laws of quantum physics endow unconditional security for information processing. However, the executions of many quantum cryptography protocols such as quantum key distribution are detectable by an adversary, who may subsequently launch, e.g., a denial-of-service attack to disrupt the data integrity. Quantum covert protocols aim to meet an elevated security criterion: the executions of the very protocols are undetectable, thereby not only protecting the secrecy but also concealing the processed information. Here, we report the theory and experiment for entanglement-enhanced covert sensing using a high-efficiency broadband entanglement source and an unconventional phase-conjugate quantum receiver. We show that entanglement offers a performance boost in estimating the imparted phase by a probed object, as compared to a classical protocol at the same covertness level. The implemented entanglement-enhanced covert sensing protocol operates close to the fundamental quantum limit by virtue of its near-optimum entanglement source and quantum receiver. Our work is expected to create ample opportunities for quantum information processing at unprecedented security and performance levels. |
Thursday, March 17, 2022 12:30PM - 12:42PM |
T39.00004: Versatile super-sensitive metrology using induced coherence William N Plick, Sven Ramelow, Nathaniel R Miller We theoretically analyze the phase sensitivity of the Induced-Coherence (Mandel-Type) Interferometer, including the case where the sensitivity is" boosted" into the bright input regime with coherent-light seeding. We find scaling which reaches below the shot noise limit, even when seeding the spatial mode which does not interact with the sample–or when seeding the undetected mode. It is a hybrid of a linear and a non-linear (Yurke-Type) interferometer, and aside from the supersensitivity, is distinguished from other systems by preferring an imbalance in the gains of the two non-linearities (with the second gain being optimal at values), and non-monotonic behavior of the sensitivity as a function of the gain of the second non-linearity. Furthermore, the setup allows use of subtracted intensity measurements, instead of direct (additive) or homodyne measurements–a significant practical advantage. Bright, super-sensitive phase estimation of an object with different light fields for interaction and detection is possible, with various potential applications, especially in cases where the sample may be sensitive to light, or is most interesting in frequency domains outside what is easily detected, or when desiring bright-light phase estimation with sensitive/delicate detectors. We use an analysis in terms of general squeezing and discover that super-sensitivity occurs only in this case–that is, the effect is not present with the spontaneous-parametric-down-conversion approximation, which many previous analyses and experiments have focused on. |
Thursday, March 17, 2022 12:42PM - 12:54PM |
T39.00005: A Michelson interferometer-based LIDAR scheme: Super-sensitivity in the presence of noise and loss Stav Haldar, Pratik J Barge, Hwang Lee Quantum Light Detection and Ranging (quantum-LIDAR) schemes show super-resolution and super-sensitivity (beating the Rayleigh and shot noise limits). This is achieved using non-classical sources like squeezed light and quantum detection apparatus such as single photon detectors. Here, we optimize the phase sensitivity of a Michelson interferometer-based LIDAR scheme under lossy and noisy conditions. We consider an entangled source in the form of a two-mode squeezed coherent state (TMSCS), which offers significant (exponential) quantum advantage for phase sensitivity over classical coherent sources. We find the maximum possible loss and thermal noise levels under which the shot noise limit can still be broken, maintaining the quantum advantage. We show that by solely controlling the squeezing angle and without changing the input power the sensitivity can be improved. This accommodates larger losses (up to 80%) than the zero-squeezing-angle case which was considered optimal prior to this work. We also compare the above optimization scheme to other possible methods like using input beams of different strengths or beam splitters with different transmissivities for input and output. Finally, we compare the noise and loss robustness of TMSCS against other entangled states as sources. |
Thursday, March 17, 2022 12:54PM - 1:06PM |
T39.00006: Temporally non-local effects in optical detection Philip D Blocher, Klaus Molmer In the quantum mechanical world every measurement performed on a system causes a curios non-classical effect, the so-called backaction. The backaction reflects our updated knowledge of the system’s state post-measurement, and in the case of a two-level system being monitored by a single photodetector, the detection of a photon causes the system to collapse on its ground state. The monitoring of quantum systems via photodetection is vital in current and emerging quantum technologies, allowing for, e.g., high precision estimation of system parameters, quantum feedback control, and heralding of certain system events of interest. |
Thursday, March 17, 2022 1:06PM - 1:18PM |
T39.00007: Diverging quantum speed limits: a herald of classicality Pablo M Poggi, Steve Campbell, Sebastian Deffner When is the quantum speed limit (QSL) really quantum?. Typically, a vanishing QSL time is an indicator of an emergent classicality. However, it is still not entirely understood what precise aspects of classicality lead to diverging quantum speeds. Here, we show that vanishing QSL times (or, equivalently, diverging quantum speeds) can be traced back to reduced uncertainty in quantum observables. We illustrate this mechanism by developing a QSL formalism for continuous variable quantum systems undergoing general Gaussian dynamics. For these systems, we show that three typical scenarios leading to vanishing QSL times, namely large squeezing, small effective Planck's constant, and large particle number, can be fundamentally connected to each other. Finally, by studying the dynamics of open quantum systems and mixed states, we show that the addition of classical noise typically increases the QSL time. |
Thursday, March 17, 2022 1:18PM - 1:30PM |
T39.00008: Limits and opportunities of the quantum radar Robert Jonsson, Martin Ankel From the field of inference and sensing with quantum systems, and quantum hypothesis testing in particular, we find the concepts of quantum radar. By exploiting entanglement to yield an advantage over classical setups, quantum radar has made headlines within the community and industries working with conventional radar. While it is generally understood that this advantage is not universal, the application space for a hypothetical device realizing it is actually severely restricted. In this work, we clarify the setting of a quantum radar in the context of quantum illumination and quantify the performance of such a device, in terms of radar operation in the microwave regime, compared to existing radar systems. Additionally, we discuss possible non-traditional, short-range applications to microwave radar. Our principal result is that it is unlikely a quantum radar based on quantum illumination will ever compete on equal footing with a conventional system for reasons fundamental rather than technological. To emphasize this result, we also comment on various technological possibilities and challenges in constructing a microwave quantum radar. |
Thursday, March 17, 2022 1:30PM - 1:42PM |
T39.00009: Swap-test interferometry with biased ancilla noise Ondrej Cernotik, Iivari Pietikäinen, Shruti Puri, Steven M Girvin, Radim Filip The Mach–Zehnder interferometer is a powerful device for detecting small phase shifts between two light beams. Simple input states—such as coherent states or single photons—can reach the standard quantum limit of phase estimation while more complicated states can be used to reach Heisenberg scaling; the latter, however, require complex states at the input which are difficult to prepare. Highly sensitive phase estimation therefore calls for interferometers with nonlinear devices which would make the preparation of such states more efficient. We show that the Heisenberg scaling can be recovered with simple input states (Fock and coherent states) when linear mirrors in the interferometer are replaced with controlled-swap gates and measurements on ancilla qubits. These swap tests project the input Fock and coherent states onto NOON and entangled coherent states, respectively, leading to improved sensitivity to small phase shifts. We perform detailed analysis of ancilla errors, showing that biasing the ancilla towards phase flips offers a great advantage, and perform thorough numerical simulations of a possible implementation in circuit quantum electrodynamics. Our results thus present a viable approach to phase estimation approaching Heisenberg-limited sensitivity. |
Thursday, March 17, 2022 1:42PM - 1:54PM |
T39.00010: Most continuous-variable quantum networks are useful for quantum metrology. Hyukgun Kwon Distributed quantum sensing is one of the quantum metrological tasks that exploit entanglement to estimate parameters in distant nodes. Until now, it is well known that particular continuous-variable (CV) quantum networks provide enhancement for distributed sensing but it is not clear whether a general quantum network is beneficial. In this work, we investigate the quantum metrological usefulness of typical CV quantum networks. Particularly, we show that most CV quantum networks provide entanglement between modes that enables one to achieve the Heisenberg scaling of an estimation error for distributed quantum displacement sensing, which cannot be attained using product states. Further, we analytically and numerically show that local phase shift operations are essential ingredients for the task. Finally, we find a tolerant photon-loss rate that maintains the quantum enhancement for practical applications. |
Thursday, March 17, 2022 1:54PM - 2:06PM |
T39.00011: Towards an Experimental Demonstration of Quantum Advantage With Microwave Quantum Illumination Réouven Assouly, Rémy Dassonneville, Audrey Bienfait, Benjamin Huard The concept of quantum illumination was introduced by Lloyd more than a decade ago. It consists in using a pair of entangled photons to probe a target located in a very noisy environment which can yield up to 4x signal to noise ratio (SNR) over the best classical setup possible despite the fact that the large amount of noise render the entanglement unobservable. In this talk, we present progress toward an experimental demonstration of this quantum advantage at microwave frequencies using a superconducting platform. The design implements the best possible classical radar as well as a quantum radar that can show up to 2x SNR improvement[1]. We use a Josepshon Parametric Converter (JPC) to generate a two-mode squeezed vacuum state. Part of this mode (the idler) is stored inside the JPC idler mode while the other (the signal) travels to and back from the target. The same JPC is used to perform a joint measurement of signal and idler. This joint measurement of idler and signal is required to see a quantum advantage and is missing in all previous attempts to demonstrate microwave quantum illumination. |
Thursday, March 17, 2022 2:06PM - 2:18PM |
T39.00012: Experimental broad range Heisenberg scaling estimation in the non-asymptotic regime Valeria Cimini, Emanuele Polino, Federico Belliardo, Francesco Hoch, Bruno Piccirillo, Bernardo Spagnolo, Vittorio Giovannetti, Fabio Sciarrino Quantum Metrology represents one of the most promising applications of quantum technologies, with the aim of using quantum resources to improve the sensitivity of quantum sensors. Here, it is crucial to reach quantum-enhanced estimation for a large resources range, a task that is still a fundamental open problem. Indeed, the states and the techniques which are commonly used to achieve such an advantage are usually too sensitive to losses. Here, we experimentally demonstrate a novel approach which allows to achieve a sub-standard-quantum-limit precision in the measurement of a rotation angle, reaching the Heisenberg scaling, for an unexplored wider range of dedicated resources. The key element to enlarge the enhanced scaling range is to properly allocate the available resources during the estimation process. Such a requirement is fulfilled by exploiting the orbital angular momentum of single photon states, scaling its value only when required by the estimation protocol. To develop such a strategy, we have implemented a new fully automatized platform composed of a series of q-plates with an increasing topological charge arranged in a cascade configuration. Such setup gives us the possibility to increase efficiently the number of total resources during the estimation procedure. |
Thursday, March 17, 2022 2:18PM - 2:30PM |
T39.00013: Fundamental Limits on Estimation of Molecular Parameters Using Entangled Photon Spectroscopy Aiman Khan, Animesh Datta Nonlinear spectroscopy using entangled photons has been shown to offer a number of apparent advantages over classical light, including increased selectivity in exciting transitions, enhanced signal-to-noise ratio of detected signal, as well as a larger set of control parameters (such as entanglement time). We recast the basic spectroscopic question of how much information about the matter system one can extract from the detected state of quantized light as that of a quantum estimation problem. By evaluating the quantum and classical Fisher informations (with respect to the parameters of interest of the matter system) of the output states of light, we can estimate the optimal input field states as well as the detection schemes for the inference problem. We illustrate this in the context of the linear biphoton spectroscopic probe of a coupled dimer system, where one of the members of an entangled photon pair (resulting from a type-II parametric down-conversion (PDC) process) couples with the matter system, and is detected in coincidence with the other photon. Under the influence of various models of the bath that coupled to the matter system, we show that the entanglement of the input probe state of light plays a role in setting these fundamental bounds. We also examine the analogous problem with other quantum states of light, as well as classical fields, to demonstrate the relative usefulness of the various probes in our estimation paradigm. |
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