Bulletin of the American Physical Society
APS March Meeting 2017
Volume 62, Number 4
Monday–Friday, March 13–17, 2017; New Orleans, Louisiana
Session P51: Novel Superconducting Circuit Readout & Qubit Systems |
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Sponsoring Units: GQI Chair: Robert Schoelkopf, Yale University Room: 398 |
Wednesday, March 15, 2017 2:30PM - 2:42PM |
P51.00001: Stroboscopic qubit measurement with injected squeezed light, Part 1: Controlling measurement backaction Sydney Schreppler, Andrew Eddins, David Toyli, Leigh Martin, Shay Hacohen-Gourgy, Luke Govia, Hugo Ribeiro, Aashish Clerk, Irfan Siddiqi As new amplification technologies permit ever faster and quieter measurements of superconducting qubits, further measurement acceleration will require alternative approaches to improve the signal-to-noise ratio achieved in a set acquisition time. Here we demonstrate the enhancement of qubit measurements using the injection of squeezed electromagnetic vacuum. Our platform combines a stroboscopic measurement technique with an interferometric configuration of parametric amplifiers to produce optimally-squeezed phase sensitive readout. In this first of two talks, we present an overview of our measurement setup and demonstrate how squeezing provides additional control over measurement backaction. We emphasize that we can slow measurement-induced dephasing by a factor of two, thereby exhibiting an important capability for future efforts toward higher fidelity multi-qubit gates. [Preview Abstract] |
Wednesday, March 15, 2017 2:42PM - 2:54PM |
P51.00002: Stroboscopic qubit measurement with injected squeezed light, Part II: Enhancing SNR Andrew Eddins, Sydney Schreppler, David Toyli, Leigh Martin, Shay Hacohen-Gourgy, Luke Govia, Hugo Ribeiro, Aashish Clerk, Irfan Siddiqi Advances in measurement and amplification technology have dramatically decreased the time needed to perform quantum nondemolition (QND) measurements of superconducting qubits. As the efficiency with which a signal can be transferred from the qubit to room-temperature approaches unity, further reductions in measurement time will require new techniques, as the measurement power is limited by the dispersive readout mechanism. Here we demonstrate how injection of electromagnetic squeezed vacuum can enhance measurement fidelity. Our platform combines a stroboscopic measurement technique with an interferometric configuration of parametric amplifiers to optimally align squeezing with our phase-sensitive readout. In this second of two talks, we present data showing SNR improvements relative to measurements performed without squeezing. We further note that under some conditions, squeezing allows us to trade off measurement speed for an increase in overall measurement efficiency. [Preview Abstract] |
Wednesday, March 15, 2017 2:54PM - 3:06PM |
P51.00003: Implementation of longitudinal qubit-ancilla coupling: a 3D V-shaped transmon R. Dassonneville, J. Puertas, L. Planat, F. Foroughi, Y. Krupko, C. Naud, W. Guichard, N. Roch, O. Buisson Despite important progresses in recent years, implementing a fast and high fidelity readout remains a major challenge in cQED. Indeed, inferring a qubit state is limited by the trade-off between speed and accuracy due to Purcell effect. To overcome this, we introduce a superconducting V-shaped artificial atom coupled to a 3D-cavity. This atom is made of two transmons coupled via a large inductance [1]. The resulting circuit presents two modes -- called qubit and ancilla -- showing a strong longitudinal coupling. Using symmetry rules [2], the ancilla can be strongly coupled to the cavity while the qubit remains unspoiled by the Purcell effect. However due to their strong longitudinal coupling, the qubit can still be inferred through the ancilla state. We will present spectroscopic evidences of the V-shape nature of our 3D circuit and its qubit-ancilla longitudinal coupling. Time domain measurements reveal relaxation and coherence times on par with other 3D architectures. Moreover our approach promises a QND readout with fidelity as high as 99.9$\%$ for a measurement time down to 60 ns [3].\\ $[1]$ E.Dumur, et al, Phys. Rev. B 92, 020515(R) (2015). \\ $[2]$ E.Dumur, et al, IEEE Trans. Appl. Supercond. 26, 1700304 (2016).\\ $[3]$ I.Diniz, et al, , Phys. Rev. A 87, 033837 (2013) [Preview Abstract] |
Wednesday, March 15, 2017 3:06PM - 3:18PM |
P51.00004: Longitudinal qubit-resonator interaction in circuit QED Philip Krantz, Simon Gustavsson, Fei Yan, Daniel L. Campbell, David Kim, Jonilyn L. Yoder, Arne L. Grimsmo, Jerome Bourassa, Alexandre Blais, Andrew J. Kerman, Terry P. Orlando, William D. Oliver We investigate an experimental implementation of a longitudinal interaction between a superconducting qubit and a half-wavelength coplanar microwave resonator. As opposed to the transverse coupling, commonly used when dispersively reading out qubits in circuit QED, the longitudinal coupling has several potential advantages, including reduced read-out times, absence of the Purcell effect, and increased signal-to-noise ratio (SNR). Instead of detecting a dispersive frequency shift of the resonator, the readout mechanism for our system is based on a parametric modulation of the qubit-resonator coupling that is on resonance with the resonator. This resonant modulation gives rise to a difference in amplitude between the two qubit states. To enhance this interaction and thus improve the state discrimination, we inductively couple the qubit to the resonator using an array of Josephson junctions placed in the center of the half-wavelength microwave resonator, which increases the participation ratio of inductance at the coupling point. I will present our latest experimental progress. [Preview Abstract] |
Wednesday, March 15, 2017 3:18PM - 3:30PM |
P51.00005: Characterizing measurement back-action in the superconducting cQED architecture Antonio D Córcoles, Chris J Wood, Jose Chavez-Garcia, Scott Lekuch, Ken Inoue, Nicholas T Bronn, Baleegh Abdo, Markus Brink, Jerry M Chow, Jay M Gambetta As superconducting qubits become increasingly reliable and scalable, more complex sequences of operations arise as part of interesting algorithms and demonstrations. Although measurements in superconducting qubits in the cQED architecture have been a standard component of quantum information processing with these devices for many years, little has been explored about the effect of a measurement operator on subsequent qubit gates. Here we present new insights on the effect of measurement on these systems and how to incorporate this learning into larger scale efforts. [Preview Abstract] |
Wednesday, March 15, 2017 3:30PM - 3:42PM |
P51.00006: In situ squeezing-enhanced qubit readout with intrinsic Purcell protection Luke C. G. Govia, Aashish A. Clerk We introduce a dispersive readout scheme for weakly coupled qubits that uses in situ two-mode squeezing to significantly enhance the signal-to-noise ratio (SNR). By generating the squeezing directly in the measurement cavity, our setup avoids the difficult task of injecting an externally prepared squeezed state with high fidelity. The scheme allows one to exponentially enhance the measurement at long times, allowing a weakly coupled system to achieve the same measurement rate as a strongly-coupled qubit in a standard dispersive measurement setup. In addition, Purcell decay of the qubit is highly suppressed in our system due to interference, implying that the system acts as its own Purcell filter. [Preview Abstract] |
Wednesday, March 15, 2017 3:42PM - 3:54PM |
P51.00007: Quantum non-demolition and high-efficiency detection of traveling microwave photons - part 1 Baptiste Royer, Arne L. Grimsmo, Jerome Bourassa, Nicolas Didier, Alexandre Blais Optical photon detectors are indispensable tools for quantum optics experiments. Realizing their microwave counterparts has, however, remained an elusive task due in part to the energy scale difference between the two frequency ranges. In this talk, we will present a possible solution to this problem by adapting a scheme for qubit readout to allow high-efficiency measurement of traveling photons. Having such photon detectors would enable a wide variety of applications ranging from quantum information processing to mesoscopic physics. [Preview Abstract] |
Wednesday, March 15, 2017 3:54PM - 4:06PM |
P51.00008: Quantum non-demolition and high-efficiency detection of traveling microwave photons - part 2 Arne L. Grimsmo, Baptiste Royer, Jérôme Bourassa, Nicolas Didier, Alexandre Blais Most proposals for continuous-in-time single-photon detectors in the microwave regime are based on the photon being absorbed in some medium, which in turn is continuously monitored to detect any change in state signaling the arrival of a photon. A major obstacle to this approach, however, is that the more strongly the medium that is intended to capture the photon is measured, the less likely this medium is to change its state, thus prohibiting the photon from entering in the first place. This paradoxical behavior is an example of the quantum Zeno effect. In this talk I will discuss how the flexibility of quantum microwave circuits offer possibilities for photodetection with no direct analogs in the optical regime and, moreover, how this allows us to bypass the problematic Zeno effect. [Preview Abstract] |
Wednesday, March 15, 2017 4:06PM - 4:18PM |
P51.00009: Two-mode squeezed light in the microwave domain Moritz Businger, Philip Krantz, Daniel Campbell, Jeffrey Grover, Archana Kamal, Fei Yan, Terry Orlando, Simon Gustavsson, William Oliver, David Hover, Vlad Bolkhovsky, Jonilyn Yoder, Chris Macklin, Kevin O'Brien, Irfan Siddiqi We present progress in measurements of two-mode squeezing at microwave frequencies using a Josephson traveling wave parametric amplifier (JTWPA). Using the parametric nature of this device, we are able to produce correlated photons separated by a frequency of 1.6 GHz. We further explore how this can be used for high fidelity readout in superconducting qubits and other high precision measurements. [Preview Abstract] |
Wednesday, March 15, 2017 4:18PM - 4:30PM |
P51.00010: Tunable Coupling Qubits For Direct Dispersive Three-Qubit Parity Measurements Alessandro Ciani, David Peter DiVincenzo A key ingredient for quantum error-correction is the ability to perform multi-qubit parity measurements. The current paradigm for these kinds of measurement is to use a quantum circuit involving CNOT gates and an ancilla qubit, that encodes the information about the parity of the string of qubits. Here we analyze how this can be done directly, ı.e., without a quantum circuit involving CNOT gates, for the case of three qubits using a dispersive readout technique. The scheme employs two measurement resonator modes and, in particular, a Tunable Coupling Qubit (TCQ) as qubit. After reviewing the input-output theory for this problem, we carefully analyze what are the conditions for which a parity measurement is possible, and how these can be matched with a TCQ. The crucial point is the flexibility in the dispersive Jaynes-Cummings parameters made possible by the TCQ, which other qubits, such as the simple Transmon, do not possess. [Preview Abstract] |
Wednesday, March 15, 2017 4:30PM - 4:42PM |
P51.00011: Scalable architecture for quantum information processing with superconducting qubits based on spin-dependent forces Pierre-Marie Billangeon, Yasunobu Nakamura We introduce a circuit implementing longitudinal spin-dependent forces with superconducting qubits, similarly to ion trap experiments. Our strategy is adapted to fixed frequency qubits, thus avoiding issues inherent to approaches based on tunable-gap qubits such as the presence of fixed quadratic couplings and an extra sensitivity to dephasing. We describe how to implement high-fidelity and fast controlled phase gates in one step. We also present a readout scheme based on a selective light-amplification mechanism induced by the simultaneous application of a spin-dependent force and a linear drive of the resonator. This method takes advantage of the nonlinearity in the bosonic contribution to the tunable interaction. We estimate the backaction on the qubit relaxation rate of a source of flux noise coupled to the circuit mediating the interaction. Our scheme can be readily adapted to transmon qubits and three-junction flux qubits. The absence of static interactions between atomic and photonic degrees of freedom naturally circumvents issues such as residual interactions, restrictions associated to the justification of the rotating wave approximation and correlated noise. This scheme can be scaled up to devise a large-scale quantum register. [Preview Abstract] |
Wednesday, March 15, 2017 4:42PM - 4:54PM |
P51.00012: Tunable Thin-Film Resonator Coupled to Two Qubits in a 3D Cavity Cody Ballard, S. K. Dutta, R. P. Budoyo, K. D. Voigt, C. J. Lobb, F. C. Wellstood We present preliminary results on using a tunable, thin-film lumped element LC resonator to couple two transmon qubits in a 3D microwave cavity. The cavity, which is used for readout, is made of aluminum and has a TE101 mode at 6.3 GHz. The LC resonator has a base frequency of about 5 GHz and the inductor contains two loops, each having a single Josephson junction. Applying magnetic flux to the loops modulates the overall inductance of the resonator allowing tuning over a 500 MHz range. Two Al/AlOx/Al transmon qubits are fabricated on the same sapphire substrate as the resonator, and are designed to have a charging energy of 200 MHz and a frequency that falls within the tuning range of the resonator. Observing the perturbations of the resonant frequencies of the qubits and the cavity as the LC resonator is tuned allows us to determine the coupling strengths between each qubit and the LC resonator and between the LC resonator and the cavity. [Preview Abstract] |
Wednesday, March 15, 2017 4:54PM - 5:06PM |
P51.00013: Frequency-tunable Quantum Dissipators Chris Wilen, Clement Wong, Naveen Nehra, Ivan Pechenezhskiy, Alex Opremcak, JJ Nelson, Caleb Howington, Britton Plourde, Maxim Vavilov, Robert McDermott We describe the design and implementation of tunable dissipative modes based on lossy nonlinear resonators. When the dissipator is tuned into resonance with a weakly damped quantum mode, the weakly damped mode relaxes at a rate that is orders of magnitude faster than its intrinsic relaxation rate. We describe the optimal parameters for realization of the tunable dissipator, and we discuss device fabrication and characterization. We examine application of the dissipator to two problems in circuit quantum electrodynamics: spurious population of the qubit 1 state and dephasing from photon shot noise in the qubit readout resonator. [Preview Abstract] |
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