Rapid High-fidelity Multiplexed Readout of Superconducting Qubits

Heinsoo, Johannes; Andersen, Christian Kraglund; Remm, Ants; Krinner, Sebastian; Walter, Theo; Salathé, Yves; Gasparinetti, Simone; Besse, Jean-Claude; Potočnik, Anton; Wallraff, Andreas; Eichler, Christopher

doi:10.1103/physrevapplied.10.034040

Cited by 226 publications

(200 citation statements)

References 57 publications

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“…The upconverted microwave pulses are routed from room temperature to the quantum device through a chain of 20 dB attenuators at the 4 K, 100 mK and 12 mK stages. We perform multiplexed readout by probing the feedline of the device with a readout pulse which has frequency components at each readout resonance frequency [42]. The readout pulses are generated and detected using an FPGA based control system (Zurich Instruments UHFQA) with a sampling rate of 1.8 GSa/s.…”

Section: Appendix B: Experimental Setup and Timing Diagrammentioning

confidence: 99%

“…Each qubit has individual charge (pink) and flux control lines (green) to perform single qubit gates and to tune the qubit transistion frequency. Each of the four qubits is coupled to an individual readout circuit used for probing the state of the qubits by frequency multiplexed dispersive readout through a common feedline (purple) [42]. Further details of the device and its fabrication are discussed in Appendix A.…”

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confidence: 99%

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Entanglement stabilization using ancilla-based parity detection and real-time feedback in superconducting circuits

et al. 2019

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Fault tolerant quantum computing relies on the ability to detect and correct errors, which in quantum error correction codes is typically achieved by projectively measuring multi-qubit parity operators and by conditioning operations on the observed error syndromes. Here, we experimentally demonstrate the use of an ancillary qubit to repeatedly measure the ZZ and XX parity operators of two data qubits and to thereby project their joint state into the respective parity subspaces. By applying feedback operations conditioned on the outcomes of individual parity measurements, we demonstrate the real-time stabilization of a Bell state with a fidelity of F ≈ 74% in up to 12 cycles of the feedback loop. We also perform the protocol using Pauli frame updating and, in contrast to the case of real-time stabilization, observe a steady decrease in fidelity from cycle to cycle. The ability to stabilize parity over multiple feedback rounds with no reduction in fidelity provides strong evidence for the feasibility of executing stabilizer codes on timescales much longer than the intrinsic coherence times of the constituent qubits.The inevitable interaction of quantum mechanical systems with their environment renders quantum information vulnerable to decoherence [1][2][3]. Quantum error correction aims to overcome this challenge by redundantly encoding logical quantum states into a larger-dimensional Hilbert space and performing repeated measurements to detect and correct for errors [4][5][6][7]. For sufficiently small error probabilities of individual operations, logical errors are expected to become increasingly unlikely when scaling up the number of physical qubits per logical qubit [8,9]. As the concept of quantum error correction provides a clear path toward fault tolerant quantum computing [10], it has been explored in a variety of physical systems ranging from nuclear magnetic resonance [11], to trapped ions [12-15] and superconducting circuits, both for conventional [16][17][18][19] and for continuous variable based encoding schemes [20].Quantum error correction typically relies on the measurement of a set of commuting multi-qubit parity operators, which ideally project the state of the data qubits onto a subspace of their Hilbert space -known as the code space -without extracting information about the logical qubit state [7]. A change in the outcome of repeated parity measurements signals the occurrence of an error, which brings the state of the qubits out of the code space. Such errors can either be corrected for in real-time by applying conditional feedback, or by keeping track of the measurement outcomes in a classical register to reconstruct the quantum state evolution in post-processing. The latter approach -also known as Pauli frame updating [21] -has the advantage of avoiding errors introduced by imperfect feedback and additional decoherence due to feedback latency. Real-time feedback, on the other hand, could be beneficial in the presence of * These authors contributed equally to this work. asymmetric relaxation e...

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Section: Appendix B: Experimental Setup and Timing Diagrammentioning

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Entanglement stabilization using ancilla-based parity detection and real-time feedback in superconducting circuits

et al. 2019

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“…These amplifiers are built around the parametric interaction between three waves called signal, pump and idler. However despite significant advances allowing improved bandwidth [13,14] and saturation power [15][16][17][18], JPA's are still insufficient for demanding applications such as multiplexed readout of qubits [19,20] or KID arrays [21].…”

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Photonic-Crystal Josephson Traveling-Wave Parametric Amplifier

et al. 2020

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An amplifier combining noise performances as close as possible to the quantum limit with large bandwidth and high saturation power is highly desirable for many solid state quantum technologies such as high fidelity qubit readout or high sensitivity electron spin resonance for example. Here we introduce a new Traveling Wave Parametric Amplifier based on Superconducting QUantum Interference Devices. It displays a 3 GHz bandwidth, a −102 dBm 1-dB compression point and added noise near the quantum limit. Compared to previous state-of-the-art, it is an order of magnitude more compact, its characteristic impedance is in-situ tunable and its fabrication process requires only two lithography steps.The key is the engineering of a gap in the dispersion relation of the transmission line. This is obtained using a periodic modulation of the SQUID size, similarly to what is done with photonic crystals. Moreover, we provide a new theoretical treatment to describe the non-trivial interplay between non-linearity and such periodicity. Our approach provides a path to co-integration with other quantum devices such as qubits given the low footprint and easy fabrication of our amplifier. arXiv:1907.10158v1 [cond-mat.mes-hall]

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“…From the measured histograms ( Figure 5) we extract readout fidelities of 89.4% and 83.3%. While these fidelities do not match the best results achieved for other quantum-limited amplifiers [32,33], we believe that they demonstrate the KIT promise for superconducting qubit readout, particularly for those situations that benefit from its broad bandwidth and high saturation power. The fidelities reported here are limited by the low gain of present KIT devices and the use of a qubit device not optimized for high-fidelity readout (κ 2χ ≈ 2 MHz).…”

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confidence: 57%

Kinetic inductance traveling-wave amplifiers for multiplexed qubit readout

Ranzani

Bal

Fong

et al. 2018

Applied Physics Letters

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We describe a kinetic inductance traveling-wave (KIT) amplifier suitable for superconducting quantum information measurements and characterize its wideband scattering and noise properties. We use mechanical microwave switches to calibrate the four amplifier scattering parameters up to the device input and output connectors at the dilution refrigerator base temperature and a tunable temperature load to characterize the amplifier noise. Finally, we demonstrate the high fidelity simultaneous dispersive readout of two superconducting transmon qubits. The KIT amplifier provides low-noise amplification of both readout tones with readout fidelities of 83% and 89% and negligible effect on qubit lifetime and coherence.

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Rapid High-fidelity Multiplexed Readout of Superconducting Qubits

Cited by 226 publications

References 57 publications

Entanglement stabilization using ancilla-based parity detection and real-time feedback in superconducting circuits

Entanglement stabilization using ancilla-based parity detection and real-time feedback in superconducting circuits

Photonic-Crystal Josephson Traveling-Wave Parametric Amplifier

Kinetic inductance traveling-wave amplifiers for multiplexed qubit readout

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