Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session H28: Qubit Readout and Open SystemsFocus
|
Hide Abstracts |
Sponsoring Units: DQI Chair: Archana Kamal Room: BCEC 161 |
Tuesday, March 5, 2019 2:30PM - 3:06PM |
H28.00001: Nonequilibrium thermodynamics and many-body dynamics in open quantum systems Invited Speaker: Masahito Ueda Quantum gas microscopy has revolutionarized our view on quantum many-body systems where atoms trapped in an optical lattice can be observed in real time at the single-particle level. At such extreme precision, the measurement backaction due to Heisenberg's uncertainty relation can no longer be ignored. One should naturally led to the question of whether or not nonequilibrium thermodynamics and statistical physics should be modified be modified and, if so, in what way and, in particular, how thermalization proceeds under continuous observation. A similar situation has emerged in a system of superconducting qubits under feedback control. I will address these issues and closely related problems of thermalization, heating and many-body localization in isolated and open quantum systems. |
Tuesday, March 5, 2019 3:06PM - 3:18PM |
H28.00002: Multiplexed Readout of Superconducting Qubits in 3D cQED Architecture Using Impedance Engineered Broadband JPA Suman Kundu, Nicolas Gheeraert, Sumeru Hazra, Tanay Roy, Kishor Salunkhe, Meghan P. Patankar, Rajamani Vijayaraghavan We propose and demonstrate a frequency-multiplexed readout scheme in 3D cQED architecture. We use four transmon qubits coupled to individual rectangular cavities which are aperture-coupled to a single rectangular waveguide feedline. A coaxial to waveguide transformer at the other end of the feedline allows to launch and collect the multiplexed signal. The reflected readout signal is amplified by an impedance engineered broadband parametric amplifier with 380 MHz of bandwidth. This provides us high fidelity single-shot readout of multiple qubits using compact microwave circuitry, an efficient way for scaling up to more qubits in 3D cQED. We also discuss possible designs for multiplexing larger number of qubits. Finally, we discuss the saturation properties of our broadband JPA and explore a few approaches to improve them to increase the number of qubits that can be measured simultaneously. |
Tuesday, March 5, 2019 3:18PM - 3:30PM |
H28.00003: Increasing qubit readout fidelity and efficiency with two-mode squeezed light Xi Cao, Gangqiang Liu, Tzu-Chiao Chien, Pinlei Lu, Michael Hatridge Implementing quantum information processing on a large scale with flawed components requires highly efficient, quantum non-demolition (QND) qubit readout. In superconducting circuits, qubit readout using coherent light with fidelity above 99% has been achieved by using a quantum-limited parametric amplifier such as the Josephson Parametric Converter (JPC), as the first stage amplifier. However, further improvement of such measurement is fundamentally limited by the vacuum fluctuations on the ports of the JPC. Alternatively, readout with squeezed input can entangle the vacuum fluctuations in different modes, thus allowing for the reduction of the noise by controlling their interference. In this talk, we demonstrate a dispersive qubit readout scheme which exploits the two-mode squeezed light generated by a first JPC and processed by a second JPC to form an amplified interferometer [1]. We have observed a 22% improvement in the voltage Signal-to-Noise Ratio (SNR) of the measurement compared to coherent light. We can also extend this scheme to generate remote entanglement. We will discuss how the role of losses changes in this system for coherent vs two-mode squeezed light. |
Tuesday, March 5, 2019 3:30PM - 3:42PM |
H28.00004: cross-resonance-based readout scheme of a superconducting flux qubit Fumiki Yoshihara, Sahel Ashhab, Tomoko Fuse, Kouichi Semba We propose a cross-resonance-based readout scheme of a superconducting flux qubit, in which a flux qubit is coupled to a resonator, and a microwave flux pulse tuned to the resonator is applied to the flux qubit. At the optimal flux bias, the persistent current of the flux qubit is an increasing or decreasing function of the flux bias, depending on the state of the qubit. When a microwave flux drive is applied to the qubit, the phase of the induced microwave signal felt by the resonator depends on the state of the qubit, and the difference between the two values is 180 degrees. Since this qubit-state-dependent phase difference is larger than that of dispersive-interaction schemes [1], the proposed cross-resonance-based readout scheme has the potential to be faster. The proposed scheme takes advantage of the large contrast of the flux-bias dependence of the persistent current, and, hence, faster readout is expected compared to the alternative readout schemes [2, 3], which are mainly for transmon qubits. |
Tuesday, March 5, 2019 3:42PM - 3:54PM |
H28.00005: Continuous joint measurement of two-qubit fluorescence: quantum dynamics and entanglement Philippe Lewalle, Andrew N Jordan We consider a continuous weak measurement scheme in which two qubit-cavity systems are allowed to fluoresce, and their fluorescence signals are mixed before being routed to a measurement apparatus. We theoretically investigate the stochastic quantum trajectories, qubit state dynamics, and entanglement dynamics between the qubits under such a joint-measurement scheme. Equivalent systems should be experimentally realizable with existing circuit-QED technologies. |
Tuesday, March 5, 2019 3:54PM - 4:06PM |
H28.00006: High-fidelity detection of information encoded in bosonic modes: Part I Christopher Wang, Salvatore Elder, Philip Reinhold, Connor Hann, Kevin S Chou, Brian J Lester, Serge Rosenblum, Christopher J Axline, Luigi Frunzio, Liang Jiang, Robert J Schoelkopf Qubit measurements in a computational basis are a necessary component of quantum computation. Examples include measurement at the end of a quantum algorithm and projective measurements during teleported operations. Although qubit readout suffers from errors, they may be repeated if the readout is quantum non-demolition (QND). In this way, individual imperfect readouts can be combined via methods such as majority voting to form a more accurate measurement. The measurement fidelity will be limited, however, by state transitions between qubit basis states. For two-level qubits, a single relaxation event destroys the information in the qubit. An increased distance in the Hilbert space between basis states for qubits encoded in bosonic modes, however, exponentially suppresses this infidelity limit due to transitions. In this talk, we present a measurement scheme in the circuit quantum electrodynamics (cQED) platform that utilizes repeated QND readouts to suppress measurement infidelity due to both individual readout errors and relaxation. [1] We characterize the fidelity of this scheme in terms of experimental parameters for various encodings. |
Tuesday, March 5, 2019 4:06PM - 4:18PM |
H28.00007: High-fidelity detection of information encoded in bosonic modes: Part II Salvatore Elder, Christopher Wang, Philip Reinhold, Connor Hann, Kevin S Chou, Brian J Lester, Serge Rosenblum, Christopher J Axline, Luigi Frunzio, Liang Jiang, Robert J Schoelkopf Single-shot qubit measurement is vital for universal quantum computation. In the field of superconducting qubits, much progress has been made in the readout and amplification chain; nonetheless, state-of-the-art measurement fidelities are limited by relaxation and detector inefficiency to about 99%. We present an experimental demonstration of a recent proposal [Hann et al, Phys. Rev. A 98, 022305] to improve measurement fidelities by orders of magnitude. By combining repeated QND measurements with error-tolerant encodings, we suppress the effects of both relaxation and detector inefficiency. The results are compared with theoretical predictions and achievable limits are described. |
Tuesday, March 5, 2019 4:18PM - 4:30PM |
H28.00008: Design of a Cryogenic, Digital Measurement Circuit for Superconducting Qubits Caleb Howington, Alexander Opremcak, Alex Kirichenko, Oleg Mukhanov, Robert F McDermott, Britton L Plourde As superconducting quantum processors increase in size and complexity, the scalability of standard techniques for qubit control and readout becomes a limiting factor. One vision for a scalable architecture leverages cryogenic, classical control and readout circuitry based on the SFQ (Single Flux Quantum) logic family. Conventional heterodyne readout uses a quantum-limited cryogenic amplifier chain and requires bulky microwave components with multiple rf lines and pump signals, with the result accessible in software at room temperature. An alternative method involves mapping the qubit state onto the photon occupation in a microwave cavity, followed by photon detection using a Josephson Photomultiplier (JPM). The result is stored as a classical circulating current. To convert this current to digital logic, a ballistic Josephson Transmission Line (JTL) can be inductively coupled to the JPM. Fluxons in the JTL are delayed depending on the circulating current in the JPM. A delay detection circuit converts arrival time to a logical 1 or 0. This digital result can then be used by a proximal classical coprocessor performing quantum error detection. Simulations and experimental results with this measurement technique will be discussed. |
Tuesday, March 5, 2019 4:30PM - 4:42PM |
H28.00009: Measuring qubit quasi-probability distributions behind out-of-time-ordered correlators Razieh Mohseninia, Jose Raul Gonzalez Alonso, Mordecai Waegell, Nicole Yunger Halpern, Justin Dressel The non-classicality of the quasi-probability distribution (QPD) behind an out-of-time-ordered correlator (OTOC) is a more nuanced witness for information scrambling than the OTOC itself. We use the method introduced in Phys. Rev. A 98, 012132 (2018) to provide different experimental protocols for obtaining such a QPD in a multi-qubit system. We show that by strategically averaging sequential measurements of any strength, we can reconstruct both OTOCs and QPDs in spite of disturbances caused by intermediate strong measurements. |
Tuesday, March 5, 2019 4:42PM - 4:54PM |
H28.00010: Time-resolved single-shot single-gate RF spin readout in silicon Prasanna Pakkiam, Andrey V. Timofeev, Matthew House, Mark Hogg, Takashi Kobayashi, Matthias Koch, Sven Rogge, Michelle Y Simmons For solid-state spin qubits, single-gate RF readout can minimise the number of gates required for scale-up since the readout sensor can integrate into the existing gates used to manipulate the qubits [1][2]. However, state of the art topological error correction codes benefit from the ability to resolve the qubit state within single-shot, that is, without repeated measurements [3]. Here we show single-gate, single-shot readout of a singlet-triplet spin state in silicon, with an average readout fidelity of 82.9% at 3.3kHz measurement bandwidth. We use this technique to measure a triplet T- to singlet S0 relaxation time of 0.62ms in precision P-donor quantum dots. We also show that the use of RF readout does not impact the spin lifetimes (S0 to T- decay remained 2ms at zero detuning). This establishes single-gate sensing as a viable readout method for spin qubits. |
Tuesday, March 5, 2019 4:54PM - 5:06PM |
H28.00011: Radio-frequency reflectometry of a quantum dot using an ultra-low-noise SQUID amplifier Felix Schupp, Natalia Ares, Aquila Mavalankar, Jonathan Griffiths, Geb Jones, Ian Farrer, David A Ritchie, Charles G Smith, George Andrew Davidson Briggs, Edward Laird Fault-tolerant spin-based quantum computers will require fast and accurate qubit readout. This can be achieved using radio-frequency reflectometry given sufficient sensitivity to the change in quantum capacitance associated with the qubit states. Here, we demonstrate a 23-fold improvement in capacitance sensitivity by supplementing a cryogenic semiconductor amplifier with a SQUID preamplifier. The SQUID amplifier operates at a frequency near 200 MHz and achieves a noise temperature below 550 mK when integrated into a reflectometry circuit, which is within a factor 115 of the quantum limit. It enables a record sensitivity to capacitance of 0.07 aFHz-0.5 and a sensitivity to oscillating charge of 5.9 x 10-24CHz-0.5. We use this circuit to measure the stability diagram of a gate-defined quantum dot, and show that the sensitivity should be sufficient for single-shot readout of a singlet-triplet qubit in GaAs without a charge sensor. |
Tuesday, March 5, 2019 5:06PM - 5:18PM |
H28.00012: Advantages of Independent Heat Sinking of a Two-Stage Cryogenic Amplifier for Quantum Dot Readout Joelle Corrigan, Trevor Knapp, John Dodson, Nathan Holman, Brandur Thorgrimsson, Thomas McJunkin, Samuel Neyens, E. R. MacQuarrie, Ryan Foote, Lisa Edge, Susan Coppersmith, Mark Alan Eriksson Reduced device electron temperature while using a cryogenic HEMT amplifier is achieved by moving the amplifier to an adjacent PCB electrically connected to the sample PCB. The amplifier PCB is directly heat sunk to the mixing chamber of a dilution refrigerator, and connects to the sample through a short stainless steel coax. Using straightforward measurements of gain and RMS noise, the two stages are tuned separately to minimize the input-referred noise for a given level of power dissipation. A single shot measurement with 650 ns rise time using 10 µW of power results in a 2.3:1 SNR and 150mK electron temperature. An electron temperature of 115 mK is achieved with lower power, and the effect of these various powers on SNR is examined for bandwidths of 540kHz and 170kHz. The large amplifier bandwidth enables high frequency lock-in measurements, resulting in lower noise data than possible without such an amplifier. The ease of use of cryogenic amplification combined with relatively low electron temperature and large bandwidth provides a useful tool for characterization of semiconductor quantum dot qubits. |
Tuesday, March 5, 2019 5:18PM - 5:30PM |
H28.00013: Fast high fidelity qubit readout of a transmon molecule using longitudinal coupling Vladimir Milchakov, Remy Dassonneville, Olivier Buisson, Luca Planat, Sébastien Leger, Javier Puertas, Karthik Srikanth Bharadwaj, Farshad Foroughi, Cecile Naud, Wiebke Hasch-Guichard, Nicolas Roch The most common technique of qubit readout in cQED relies on the transverse dispersive coupling between a qubit and a microwave cavity. However, despite important progresses, implementing fast high fidelity readout remains a major challenge. Indeed, inferring the qubit state is limited by the trade-off between speed and accuracy due to Purcell effect and unwanted transitions induced by readout photons in the cavity. To overcome this, we introduce a transmon molecule based on two transmons coupled by a large inductance, which is inserted inside a 3D-cavity. The full system presents one transmon –used as qubit– with a large direct cross-Kerr(longitudinal) coupling to a non-linear readout resonator, called polaron mode. This polaron mode results from the hybridization between the microwave cavity and the second mode of the transmon molecule circuit. The direct cross-Kerr coupling is a key point of our readout scheme since it protects the qubit from Purcell effect. We will present qubit readout performance with fidelity as high as 95.7% in 120ns and discuss the quantum non-demolition properties of this novel readout. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700