Bulletin of the American Physical Society
APS March Meeting 2023
Volume 68, Number 3
Las Vegas, Nevada (March 5-10)
Virtual (March 20-22); Time Zone: Pacific Time
Session T71: Quantum Reservoir Engineering and Non-Reciprocal InteractionsFocus
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Sponsoring Units: DQI Chair: Gerry Angelatos, BBN Technology - Massachusetts Room: Room 407/408 |
Thursday, March 9, 2023 11:30AM - 11:42AM |
T71.00001: Weak measurement feedback and Zeno pinning for remote entanglement generation and stabilization in superconducting qubits Sacha R Greenfield, Leigh S Martin, Felix Motzoi, Birgitta Whaley, Justin G Dressel, Eli Levenson-Falk Superconducting qubits are one of the most promising qubit technologies due to their balance of addressability (ability to couple to their environment) and coherence (ability to isolate from the environment). Weak measurement utilizes weak probes of a readout resonator coupled to the qubit in order to gain small amounts of information about the qubit state, leading to diffusive trajectories in Hilbert space. This is a valuable tool for state preparation and control because it allows for unitary feedback as the measurement takes place. |
Thursday, March 9, 2023 11:42AM - 11:54AM |
T71.00002: Noise suppression in superconducting qubits through on-demand cavity cooling and optimal control Haimeng Zhang, Darian M Hartsell, Evangelos Vlachos, Sacha R Greenfield, Azarin Zarassi, Vivek Maurya, Clark Miyamoto, Jocelyn Liu, James T Farmer, Daria Kowsari, Kater Murch, Daniel A Lidar, Eli Levenson-Falk Noise suppression techniques that extend qubit lifetimes, such as reservoir engineering and optimal control, are crucial ingredients for NISQ-era superconducting quantum devices. While control techniques such as dynamical decoupling have been widely adopted in compiling circuits to run quantum algorithms, so far, few experimental studies have co-designed a qubit's control pulses with its dissipative environment. We design a transmon qubit with an effective tunable environment by coupling its readout resonator to an auxiliary lossy mode. We experimentally test that we can effectively remove spurious excitation from the qubit's environment on-demand through a parametrically driven coupling. Furthermore, we study the qubit noise characteristics and explore optimal control strategies for suppressing the engineered, tunable bath. We anticipate that this work will provide insights into noise suppression in superconducting qubits both on the hardware and software levels. |
Thursday, March 9, 2023 11:54AM - 12:06PM |
T71.00003: Efficient superconducting qubit measurement with an integrated nonreciprocal amplifier Benton T Miller, Florent Q Lecocq, Bradley Hauer, Katarina Cicak, Raymond W Simmonds, John D Teufel, Jose Aumentado In a typical dispersive superconducting qubit readout, circulators are placed between the readout cavity and quantum limited amplifier to avoid amplifier backaction on the qubit. However, losses due to the circulators and associated wiring significantly reduce the measurement efficiency, limiting single-shot readout fidelity and restricting the viability of weak measurement-based feedback protocols. Using a nonreciprocal amplifier can alleviate the need for circulators, enabling a more scalable and efficient measurement chain [1]. Here we discuss the operation of an integrated system combining a transmon qubit, a readout cavity and a nonreciprocal amplifier in a 3D structure. Using either continuous wave or pulsed operation, we show that this system enables high-efficiency and low backaction qubit measurement. |
Thursday, March 9, 2023 12:06PM - 12:18PM |
T71.00004: Passive superconducting circulator on a chip Arkady Fedorov An on-chip microwave circulator that is compatible with superconducting devices is a key element for scale-up of superconducting circuits. Previous approaches to integrating circulators on chip involve either external driving that requires extra microwave lines or a strong magnetic field that would compromise superconductivity. Here we report the first proof-of-principle realisation of a passive on-chip circulator which is made from a superconducting loop interrupted by three notionally-identical Josephson junctions and is tuned with only DC control fields. Our experimental results shows evidence for nonreciprocal scattering, and excellent agreement with theoretical simulations. We also present a detailed analysis of quasiparticle tunneling in our device using a hidden Markov model. By reducing the junction asymmetry and utilising the known methods of protection from quasiparticles, we anticipate that Josephson-loop circulator will become ubiquitous in superconducting circuits. |
Thursday, March 9, 2023 12:18PM - 12:30PM |
T71.00005: Passive On-chip Microwave Circulator based on a Josephson Ring Yutaka Takeda, Yutaka Tabuchi, Shuhei Tamate, Shumpei Masuda, Shingo Kono, Yasunobu Nakamura Scaling up superconducting quantum computers requires downsized and integrated readout circuits of qubits. In particular, conventional nonreciprocal devices such as ferrite-based circulators and isolators are bulky and difficult to incorporate into chips. As alternatives to ferrite circulators, on-chip circulators realized through a time-dependent microwave drive have been demonstrated. However, it is more desirable to get rid of the drive fields for better scalability. Here, we present a passive on-chip microwave circulator based on a Josephson ring circuit. The circuit design has been improved from the original theoretical proposal for experimental feasibility. Particularly, the reduction of the number of relevant modes enables impedance matching with experimentally feasible parameters. We observe microwave nonreciprocity of the Josephson ring device in transmission spectra. We further investigate the microwave response as a function of the gate charge and external flux to the circuitry, showing a good agreement with the theory. We discuss the limiting factors of the circulator's performance focusing mainly on the effect of charge parity switching due to quasi-particle tunneling. |
Thursday, March 9, 2023 12:30PM - 1:06PM |
T71.00006: Unbounded deterministic entanglement generation by autonomous quantum measurement and feedforward Invited Speaker: Yuxin Wang Entanglement generation is crucial for the implementation of a plethora of quantum information processing tasks. Open quantum dynamics, including dissipation and measurements, provides a versatile approach to producing entanglement. However, standard open-system entangling schemes either require post-selection or conditional feedback, or focus on the stationary state regime, where the maximal amount of entanglement is ultimately set by parameters describing the dissipative process (i.e. the Liouvillian). Here, we propose a class of dissipative protocols, based on autonomous quantum measurement and feedforward, where the entanglement generation is deterministic, and can even grow indefinitely with evolution time in bosonic systems. While such entanglement exhibits a curious tradeoff with purity of the generated states, we also show how pure-state entanglement can be deterministically recovered via a single cycle of local measurement and feedback operations. Our results reveal a pathway for converting measurement-induced conditional entanglement into deterministic entanglement, and also shed new light on the entanglement generation mechanism via correlated dephasing. Furthermore, our feedforward-based approach opens up new possibilities of probing measurement-induced entanglement phase transitions in unconditional dynamics. |
Thursday, March 9, 2023 1:06PM - 1:18PM |
T71.00007: Dispersive Non-reciprocity between a Qubit and a Cavity Yingying Wang, Yuxin Wang, Sean van Geldern, Thomas Connolly, Aashish A Clerk, Chen Wang Non-reciprocity is a valuable and unique property for building interesting and complex quantum systems. Previous study of non-reciprocity focuses on non-Hermitian Hamiltonian models for both linear and cascaded nonlinear systems, both of which study non-reciprocity of resonant excitation exchange. Quantum interactions between far-detuned modes are central to QIP, most prominently the reciprocal dispersive interaction. Here, we explore non-reciprocity between off-resonant quantum modes by presenting an experimental study of a non-reciprocal dispersive-type interaction between a transmon qubit and a superconducting cavity, arising from dissipative intermediary modes with broken time reversal symmetry. We characterize the qubit-cavity dynamics, including asymmetric frequency pulls and photon shot-noise dephasing, under varying degrees of non-reciprocity. Importantly, we show that the qubit-cavity dynamics can be well described for a wide parameter regime by a simple non-reciprocal master-equation model, which avoids the challenge of understanding the highly complex dynamics of the intermediary system. Our result provides an example of quantum non-reciprocal phenomena beyond the typical non-Hermitian Hamiltonian and cascaded system models. |
Thursday, March 9, 2023 1:18PM - 1:30PM |
T71.00008: Driven-dissipative dynamics in superconducting circuit lattice coupled to tunable baths Botao Du, Ramya Suresh, Qihao Guo, Ruichao Ma Quantum reservoir engineering plays a key role in understanding the influence of the environment on quantum systems. In recent years, engineered reservoirs have emerged as a powerful tool for controlling quantum systems for application in entanglement generation, autonomous quantum error correction, etc. One experimental platform to explore these ideas is superconducting circuits where high coherence, strongly interacting qubit arrays are combined with well-controlled driving and dissipation. Here, we developed a hardware-efficient approach to engineer tunable local baths, using parametrically-enabled coupling between qubits and their readout resonators which serve as reservoirs. We explore the driven dissipative dynamics in a 1D Bose-Hubbard lattice coupled to local gain/loss with tunable spectrum and strength. This architecture enabled us to study correlation across the lattice and measure transport property when baths are coupled to different locations of the lattice. Our future plan for long-range entanglement generation using non-local baths and many-body state stabilization with broadband baths will also be discussed. |
Thursday, March 9, 2023 1:30PM - 1:42PM |
T71.00009: Dissipative preparation and stabilization of quantum states in superconducting qutrit chains Yunzhao Wang, Kyrylo Snizhko, alessandro romito, Yuval Gefen, Kater Murch Dissipative processes contribute novel elements for quantum information processing when controlled and engineered. One of their vital applications is preparing a quantum manybody system into a targeted entangled state. In this talk, we propose a driven-dissipative protocol to stabilize the Affleck-Kennedy-Lieb-Tasaki (AKLT) state, a prototypical example for matrix product states and symmetry protected topological states, in a chain of superconducting qutrits. By having each two nearest neighbor qutrits sharing dispersive interaction with a linear cavity, we realize the autonomous feedback process. Via simulation, we demonstrate and analyze the creation and stabilization of the AKLT state, as well as the performance of the protocol with the system size scaling up. |
Thursday, March 9, 2023 1:42PM - 1:54PM |
T71.00010: Dissipative Pairing Interactions: Quantum Instabilities, Topological Light, and Volume-Law Entanglement Andrew Pocklington, Yuxin Wang, Aashish A Clerk It is well known that coherent bosonic pairing interactions (as described by a fully Hermitian Hamiltonian) can lead to dynamical instabilities, with the paradigmatic example being a degenerate parametric amplifier. Here, we instead study the physics of dissipative pairing interactions in a fully quantum setting. We show that in isolation, these dissipative (or non-Hermitian) interactions are dynamically stable. However, by combining a stable dissipative pairing interaction with a stable multi-mode hopping Hamiltonian, one can create a novel and potentially useful class of bosonic instabilities [1]. These pairing-induced instabilities exhibit extraordinary properties: the steady state solution remains completely pure up to the instability threshold, and there is a pronounced sensitivity to wavefunction localization. This provides a simple yet powerful method for selectively populating and entangling edge modes of topological photonic lattices, using only a single, localized, engineered reservoir; this is considerably simpler than standard methods which require complicated, non-local driving. We outline how our technique can be physically realized in a number of experimental platforms, including superconducting circuits. |
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