Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session W34: CV Quantum Computation and Simulation IIFocus Recordings Available
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Sponsoring Units: DQI Chair: Tian Zhong, University of Chicago Room: McCormick Place W-193A |
Thursday, March 17, 2022 3:00PM - 3:36PM |
W34.00001: Error correction of a logical grid state qubit by dissipative pumping Invited Speaker: Jonathan P Home Quantum error correction is expected to play an important role in the realization of large-scale quantum computers. At the lowest level, it takes advantage of embedding qubits in a larger Hilbert space, giving redundancy which allows measurements which preserve logical information while revealing the presence of errors. While many codes rely on multiple physical systems, Bosonic codes make use of the higher dimensional Hilbert space of a single harmonic oscillator mode. A powerful Bosonic code is the GKP code proposed in 2001, which uses non-local "grid" states to protect information from small displacements of an oscillator. I will describe experiments in which we encode, measure and perform quantum error correction on an encoded logical GKP qubit, using the motion of a trapped ion coupled by laser light to an electronic ancilla qubit. We introduce a measurement approach for the finite-energy GKP code which can realize high fidelity qubit readout, and use this to construct a dissipative map which performs error correction, achieving an extension of logical coherence across all logical axes of more than three. I will also show how these techniques are related laser cooling, offering a particularly efficient means of entropy extraction from the oscillator via a single spin. I will present perspectives for exending this work to multiple logical qubits as well as towards break-even. |
Thursday, March 17, 2022 3:36PM - 3:48PM |
W34.00002: Simulating a Quantum Phase Transition in the Ising Model Using a Superconducting Circuit Aaron Somoroff, Nitish Mehta, Roman Kuzmin, Maxim G Vavilov, Vladimir Manucharyan Superconducting circuits are a promising platform for analog and digital quantum computing due to their controllability and scalability. In recent years, the fluxonium circuit has emerged as an excellent qubit due to its strong anharmonicity and high coherence times [1,2]. Fluxonium can be viewed as an inductively shunted transmon, such that the inductance forms a closed loop with the phase-slip junction, giving the spectrum flux tunability. In this talk, we present our work on simulating the Transverse Field Ising Model (TFIM) using a chain of 10 inductively coupled fluxonium circuits. When biased at half-integer values of the magnetic flux quantum, the spectrum becomes highly anharmonic, and the 10-circuit hamiltonian takes the form of the TFIM [3]. By tuning the inter-qubit coupling strength across multiple devices, we explore different regimes of the TFIM, establishing fluxonium as a prominent candidate for near-term quantum simulators. |
Thursday, March 17, 2022 3:48PM - 4:00PM |
W34.00003: Squeezing-free quantum gates for GKP codes Pei Zeng, Liang Jiang The Gottesman-Kitaev-Preskill (GKP) code is a promising candidate for the quantum error correction in the bosonic-mode-based quantum information processing. One major advantage of the GKP code is that all the logical Clifford gates are Gaussian and the only non-Gaussian resource we need is the GKP state itself. However, in many bosonic systems, especially for the optical platform, even the Gaussian squeezing gate like controlled-SUM gate is hard to implement, hindering the realization of the GKP CNOT gate. |
Thursday, March 17, 2022 4:00PM - 4:12PM |
W34.00004: Towards the implementation of a logical CNOT gate between stabilized Gottesman-Kitaev-Preskill (GKP) qubits - Part 1of 2 Zhenghao Ding, Alec W Eickbusch, Benjamin L Brock, Max Hays, Volodymyr Sivak, Baptiste Royer, Ioannis Tsioutsios, Christopher Wang, Stijn de Graaf, Benjamin J Chapman, Shruti Puri, Luigi Frunzio, Robert J Schoelkopf, Michel H Devoret Bosonic error correction is a promising candidate for the realization of quantum computation in the presence of noise. Recently, the Gottesman-Kitaev-Preskill (GKP) code with logical states realized as grid states encoded in an oscillator was prepared and stabilized using repeated interactions with an ancilla qubit at ETH and Yale. To realize universal computation with the GKP encoding, or to embed the GKP code in a higher-level layer of error correction, a logical two-qubit gate is needed, such that the full Clifford group can be implemented. Here, we focus on the realization of a logical controlled-NOT gate between GKP code words stabilized in a superconducting cavity. In the first part of this two-part series, we discuss the stabilization of a GKP logical qubit and the engineering of an effective quadrature-quadrature interaction in cQED. |
Thursday, March 17, 2022 4:12PM - 4:24PM |
W34.00005: Towards the implementation of a logical CNOT gate between stabilized Gottesman-Kitaev-Preskill (GKP) qubits - Part 2of 2 Alec W Eickbusch, Zhenghao Ding, Benjamin L Brock, Max Hays, Volodymyr Sivak, Baptiste Royer, Ioannis Tsioutsios, Christopher Wang, Stijn de Graaf, Benjamin J Chapman, Shruti Puri, Luigi Frunzio, Robert J Schoelkopf, Michel H Devoret Bosonic error correction is a promising candidate for the realization of quantum computation in the presence of noise. Recently, the Gottesman-Kitaev-Preskill (GKP) code with logical states realized as grid states encoded in an oscillator was prepared and stabilized using repeated interactions with an ancilla qubit at ETH and Yale. To realize universal computation with the GKP encoding, or to embed the GKP code in a higher-level layer of error correction, a logical two-qubit gate is needed, such that the full Clifford group can be implemented. Here, we focus on the realization of a logical controlled-NOT gate between GKP code words stabilized in a superconducting cavity. In the second part of this two-part talk, we discuss the design and implementation of the quadrature-quadrature interaction needed to engineer a logical two-qubit CNOT gate between stabilized GKP codes in cQED. |
Thursday, March 17, 2022 4:24PM - 4:36PM |
W34.00006: Toward the integration of a nonreciprocal amplifier with a transmon qubit Benton T Miller, Florent Q Lecocq, Bradley Hauer, Katarina Cicak, Raymond W Simmonds, John Teufel, Jose Aumentado In typical superconducting qubit dispersive readout schemes, the measurement signal is routed from the readout cavity to the amplification chain using magnetic circulators. These circulators allow for a modular approach in which the amplifier and qubit-cavity system can be developed separately. However, their intrinsic loss and the required wiring significantly reduce the measurement efficiency and increase the system complexity and footprint. |
Thursday, March 17, 2022 4:36PM - 4:48PM |
W34.00007: Drive-induced nonlinearities of cavity modes coupled to a transmon ancilla Yaxing Zhang, Jacob C Curtis, Christopher Wang, Robert J Schoelkopf, Steven M Girvin High-Q microwave cavity modes coupled to transmon ancillas provide a hardware-efficient platform for quantum computing. Due to the coupling, the cavity modes inherit finite nonlinearity from the transmons. We theoretically and experimentally investigate how an off-resonant drive on the transmon modifies the nonlinearity of the cavity modes in qualitatively different ways, depending on the interrelation among cavity-transmon detuning, drive-transmon detuning and transmon anharmonicity. For weak transmon-cavity coupling, the cavity Kerr nonlinearity relates to the third-order nonlinear susceptibility function of the driven transmon. This susceptibility function provides an efficient way of computing the cavity Kerr particularly for systems with many cavity modes controlled by a single transmon. It also serves as a diagnostic tool for identifying undesired drive-induced multiphoton resonances. Lastly, we show that an off-resonant transmon drive with a judiciously chosen amplitude can be used to cancel the cavity self-Kerr or the inter-cavity cross-Kerr. This provides a way of dynamically correcting the cavity Kerr nonlinearity during bosonic operations and quantum error correction protocols that rely on the cavity modes being linear. |
Thursday, March 17, 2022 4:48PM - 5:00PM |
W34.00008: Parametric instability and effective non-Hermitian dynamics in a bosonic Kitaev model with Kerr nonlinearity Zheng Shi, Jimmy Shih-Chun Hung, Jamal H Busnaina, Christopher Wilson A multimode superconducting parametric cavity can efficiently simulate bosonic lattice models, whose lattice sites in synthetic dimensions are resonant modes subject to flux-induced parametric couplings. In particular, the combination of beam-splitter and downconversion couplings allows to realize a bosonic Kitaev chain, known to exhibit phase-dependent chiral transport and an effective non-Hermitian skin-effect. In this work, we theoretically study in the semiclassical framework the interplay of the intrinsic Kerr nonlinearity and the non-Hermitian dynamics in a short synthetic Kitaev chain. We focus on the coupling strength threshold for parametric instability and the above-threshold parametric oscillations, and confirm their sensitive dependence on the amplitudes and phases of the couplings at the edge. This provides an example for the non-Hermitian skin-effect in an experimentally realistic nonlinear system. |
Thursday, March 17, 2022 5:00PM - 5:12PM |
W34.00009: Reducing cavity-qubit operation times with antisymmetric pulses for bosonic codes. asaf A diringer, Shay Hacohen-Gourgy, Eliya Blumenthal Bosonic encoding is a nascent robust path to quantum computation, allowing error correction already at the hardware level. For an oscillator dispersively coupled to a two level ancilla, the universal control required for computation with any bosonic code was shown to be possible. However, the rate of control of such systems, as realized by Transmon coupled to a long-lived mode of a microwave cavity, is typically limited by the qubit-oscillator dispersive coupling strength [Heeres et al., 2017]. |
Thursday, March 17, 2022 5:12PM - 5:24PM |
W34.00010: Protected and controllable GKP qubits in high-impedance Josephson circuits. Phillipe Campagne-Ibarcq, Pierre Rouchon, Alain Sarlette, Mazyar Mirrahimi Dynamics of an oscillator governed by two commuting modular operators can stabilize the GKP code. We propose to effectively engineer these in the rotating frame of a high-impedance Josephson circuit coupled to a cold reservoir. Numerical simulations show that logical errors triggered by single-photon dissipation are then exponentially suppressed when increasing the engineered dissipation strength. Our scheme also allows for protected initialization and readout of the encoded qubits, and for a set of exact Clifford gates. |
Thursday, March 17, 2022 5:24PM - 5:36PM |
W34.00011: GKP code stabilization with robust ancilla error suppression Christian Siegele, Mazyar Mirrahimi, Philippe Campagne-Ibarcq The GKP code allows for generic error-correction of a qubit encoded in a harmonic oscillator. Recent experiments have demonstrated the stabilization of the code manifold based on Rabi interactions with an ancillary two-level system. However, these schemes suffer from uncorrectable logical flips triggered by ancilla relaxation errors during the interaction. |
Thursday, March 17, 2022 5:36PM - 5:48PM |
W34.00012: Performance of teleportation-based error correction circuits for bosonic codes with noisy measurements Timo Hillmann, Isaac Quijandria Diaz, Arne L Grimsmo, Giulia Ferrini We further analyze the error correction performance of rotation-symmetric (RSB) codes using a Knill-type error correction circuit (ECC) including measurement errors into the noise model of the data qubit. Focusing on physical measurements models, we assess the performance of heterodyne and adaptive homodyne detection in comparison to the previously studied canonical phase measurement. We find that with the current measurement efficiencies in microwave optics, RSB codes undergo a substantial decrease in their break-even potential. The results are compared to GKP codes using a similar ECC which shows a greater reduction in performance together with a vulnerability to photon dephasing. Our results show that highly efficient measurement protocols are an important part of error-corrected quantum information processing with bosonic codes. |
Thursday, March 17, 2022 5:48PM - 6:00PM |
W34.00013: Exploration of potential multi-mode architectures for 3D SRF QPUs Silvia Zorzetti, Jens Koch, Srivatsan Chakram, Davide Venturelli, Doga M Kurkcuoglu, Anna Grassellino, Alexander Romanenko Decoherence is a key limiting parameter in quantum computing that determines the lifetime of quantum states. Multi-cell superconducting (SRF) cavities with long coherence are promising devices to achieve a large computational quantum volume for a prospective quantum processor based on bosonic qubits. We present preliminary architectural studies and solutions to determine optimal multi-mode devices as quantum processing units (QPUs) via 3D circuit Quantum Electrodynamics (cQED). |
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