High-fidelity superconducting quantum processors via laser-annealing of transmon qubits

Zhang, Eric; Srinivasan, Srikanth; Sundaresan, Neereja; Bogorin, Daniela F.; Martin, Yves; Hertzberg, Jared; Timmerwilke, John; Pritchett, Emily; Yau, Jeng-Bang; Wang, Cindy; Landers, W.; Lewandowski, Eric P.; Narasgond, Adinath; Rosenblatt, Sami; Keefe, George; Lauer, Isaac; Rothwell, Mary Beth; McClure, Douglas; Dial, Oliver; Orcutt, Jason S.; Brink, Markus; Chow, Jerry M.

doi:10.48550/arxiv.2012.08475

Cited by 15 publications

(31 citation statements)

References 25 publications

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“…These requirements of simultaneously having small detunings and avoiding frequency collisions, including transitions to the second excited states, lead to a complicated frequency-allocation procedure for transmon-based processors [40]. Modern fabrica-tion techniques result in 1% imprecision in transmon frequencies [41], which is insufficient to obtain a high yield of devices that satisfy frequency conditions unless an additional post-fabrication tuning is performed [42,43].…”

Section: Discussionmentioning

confidence: 99%

Controlled-NOT gates for fluxonium qubits via selective darkening of transitions

Nesterov¹,

Wang²,

Manucharyan³

et al. 2022

Preprint

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We analyze the cross-resonance effect for fluxonium circuits and investigate a two-qubit gate scheme based on selective darkening of a transition. In this approach, two microwave pulses at the frequency of the target qubit are applied simultaneously with a proper ratio between their amplitudes to achieve a controlled-not operation. We study in detail coherent gate dynamics and calculate gate error. With nonunitary effects accounted for, we demonstrate that gate error below 10 −4 is possible for realistic hardware parameters. This number is facilitated by long coherence times of computational transitions and strong anharmonicity of fluxoniums, which easily prevents excitation to higher excited states during the gate microwave drive.

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Section: Discussionmentioning

confidence: 99%

Controlled-NOT gates for fluxonium qubits via selective darkening of transitions

Nesterov¹,

Wang²,

Manucharyan³

et al. 2022

Preprint

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“…Superconducting quantum computers with moderate numbers of qubits are already available [1][2][3][4][5]. To increase the number of qubits further, every part of the current setups needs to be improved: data artificial atoms (AAs) that encode the qubits, room-temperature electronics that controls these AAs, and the interconnect between them.…”

Section: Introductionmentioning

confidence: 99%

“…In particular, we show how to reduce the number of the needed transmission lines attached to each AA. The current designs [1][2][3][4][5] use separate lines for control and measurement of the AA. The control line is directly attached to the AA, but has a very small coupling such that the decay of the AA into this line is smaller than the other decoherence rates.…”

Section: Introductionmentioning

confidence: 99%

Saturable Purcell filter for circuit QED

Iakoupov¹,

Koshino²

2022

Preprint

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We consider a typical circuit QED setup where a data artificial atom encodes a qubit and is dispersively coupled to a measurement resonator that in turn is coupled to a transmission line. We show theoretically that by placing a filter artificial atom in this transmission line, the effective decay of the data artificial atom into the transmission line (the Purcell decay) is suppressed. When strong control fields are present in the transmission line, the filter artificial atom is saturated and hence effectively switched off. This permits both control and measurement of the data artificial atom using a single transmission line, while maintaining the Purcell filtering capability and therefore a long coherence time of the data artificial atom in the absence of the control pulses. We also apply open systems optimal control techniques to optimize the π-pulse on the data artificial atom, achieving high fidelity. The considered setup is compatible with the frequency multiplexing, potentially enabling both control and measurement of several qubits using a single Purcell-filtered transmission line. Our work helps with the scalability of the superconducting quantum computers by decreasing the ratio between the number of qubits and the number of the required transmission lines. For the setups that already use one transmission line both for measurement and control, our work provides a way to filter out the qubit frequency completely without removing the possibility of controlling the system.

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“…Superconducting qubits are a leading platform for quantum computing 1,2 . This has been driven, in part, by improvements in coherence times over five orders of magnitude since the realization of coherent dynamics in a cooper pair box 3 .…”

Section: Introductionmentioning

confidence: 99%

Dynamics of superconducting qubit relaxation times

Carroll¹,

Rosenblatt²,

Jurcevic³

et al. 2021

Preprint

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Superconducting qubits are a leading candidate for quantum computing but display temporal fluctuations in their energy relaxation times T 1 . This introduces instabilities in multi-qubit device performance. Furthermore, autocorrelation in these time fluctuations introduces challenges for obtaining representative measures of T 1 for process optimization and device screening. These T 1 fluctuations are often attributed to time varying coupling of the qubit to defects, putative two level systems (TLSs). In this work, we develop a technique to probe the spectral and temporal dynamics of T 1 in single junction transmons by repeated T 1 measurements in the frequency vicinity of the bare qubit transition, via the AC-Stark effect. Across 10 qubits, we observe strong correlations between the mean T 1 averaged over approximately nine months and a snapshot of an equally weighted T 1 average over the Stark shifted frequency range. These observations are suggestive of an ergodiclike spectral diffusion of TLSs dominating T 1 , and offer a promising path to more rapid T 1 characterization for device screening and process optimization.

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High-fidelity superconducting quantum processors via laser-annealing of transmon qubits

Cited by 15 publications

References 25 publications

Controlled-NOT gates for fluxonium qubits via selective darkening of transitions

Controlled-NOT gates for fluxonium qubits via selective darkening of transitions

Saturable Purcell filter for circuit QED

Dynamics of superconducting qubit relaxation times

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