Materials in superconducting quantum bits

Oliver, William; Welander, Paul B.

doi:10.1557/mrs.2013.229

Cited by 251 publications

(194 citation statements)

References 87 publications

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“…This value of ffiffiffiffiffiffi A Φ p is on the high side of the range observed for flux-tunable SIS transmons [49][50][51][52]. White flux noise has not been reported in these more standard systems.…”

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confidence: 81%

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Evolution of Nanowire Transmon Qubits and Their Coherence in a Magnetic Field

et al. 2018

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confidence: 81%

“…Using a persistent current mode for the solenoid providing B k , we aim to investigate the spectrum and coherence of flux-tunable transmons in B k . This could yield further insight into the microscopic origin of 1=f flux noise [52]. Studying the temperature and B k behavior of the observed charge traps may lead to further understanding of their nature.…”

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confidence: 88%

Evolution of Nanowire Transmon Qubits and Their Coherence in a Magnetic Field

et al. 2018

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“…This assertion reflects, in part, several successes over the past decade addressing the fundamental operability of this qubit modality [1][2][3]. A partial list includes a 5-orders-of-magnitude increase in the coherence time T 2 [4], the active initialization of qubits in their ground state [1,5], the demonstration of low-noise parametric amplifiers [6][7][8][9][10][11][12] enabling high-fidelity readout [13][14][15][16], and the implementation of a universal set of high-fidelity gates [17]. In addition, prototypical quantum algorithms [18][19][20] and simulations [21,22] have been demonstrated with few-qubit systems, and the basic parity measurements underlying certain error detection protocols are now being realized with qubit stabilizers [23][24][25][26][27][28] and photonic memories [29].…”

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confidence: 96%

Thermal and Residual Excited-State Population in a 3D Transmon Qubit

et al. 2015

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Remarkable advancements in coherence and control fidelity have been achieved in recent years with cryogenic solid-state qubits. Nonetheless, thermalizing such devices to their milliKelvin environments has remained a long-standing fundamental and technical challenge. In this context, we present a systematic study of the first-excited-state population in a 3D transmon superconducting qubit mounted in a dilution refrigerator with a variable temperature. Using a modified version of the protocol developed by Geerlings et al., we observe the excited-state population to be consistent with a Maxwell-Boltzmann distribution, i.e., a qubit in thermal equilibrium with the refrigerator, over the temperature range 35-150 mK. Below 35 mK, the excited-state population saturates at approximately 0.1%. We verified this result using a flux qubit with ten times stronger coupling to its readout resonator. We conclude that these qubits have effective temperature T eff ¼ 35 mK. Assuming T eff is due solely to hot quasiparticles, the inferred qubit lifetime is 108 μs and in plausible agreement with the measured 80 μs. Superconducting qubits are increasingly promising candidates to serve as the logic elements of a quantum information processor. This assertion reflects, in part, several successes over the past decade addressing the fundamental operability of this qubit modality [1][2][3]. A partial list includes a 5-orders-of-magnitude increase in the coherence time T 2 [4], the active initialization of qubits in their ground state [1,5], the demonstration of low-noise parametric amplifiers [6][7][8][9][10][11][12] enabling high-fidelity readout [13][14][15][16], and the implementation of a universal set of high-fidelity gates [17]. In addition, prototypical quantum algorithms [18][19][20] and simulations [21,22] have been demonstrated with few-qubit systems, and the basic parity measurements underlying certain error detection protocols are now being realized with qubit stabilizers [23][24][25][26][27][28] and photonic memories [29].Concomitant with these advances is an enhanced ability to improve our understanding of the technical and fundamental limitations of single qubits. The 3D transmon [30] has played an important role in this regard, because its relatively clean electromagnetic environment, predominantly low-loss qubit-mode volume, and resulting long coherence times make it a sensitive test bed for probing these limitations.One such potential limitation is the degree to which a superconducting qubit is in equilibrium with its cryogenic environment. Consider a typical superconducting qubit with a level splitting E ge ¼ hf ge , with f ge ¼ 5 GHz, mounted in a dilution refrigerator at temperature T ¼ 15 mK, such that E ge ≫ k B T. Ideally, such a qubit in thermal equilibrium with the refrigerator will have a thermal population P jei ≈ 10 −5 % of its first excited state according to Maxwell-Boltzmann statistics. In practice, however, the empirical excited-state population reported for various superconducting qubits (featuring similar...

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“…An advantage of the superconducting qubit is that such a quantum system with desired circuit parameters can be designed and fabricated. As a result of many efforts to improve the decoherence time of the qubit, sub-ms decoherence time has now been achieved [39]. One recent trend regarding the superconducting qubit is to realize large-scale systems with many qubits; thus, improvement of the scalability is crucial, as is a longer decoherence time.…”

Section: Superconducting Quantum Computersmentioning

confidence: 99%

Phase Shift and Control in Superconducting Hybrid Structures

Yamashita

2018

IEICE Trans. Electron.

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Taro YAMASHITA†, † †a) , Member SUMMARYThe physics and applications of superconducting phase shifts and their control in superconducting systems are reviewed herein. The operation principle of almost all superconducting devices is related to the superconducting phase, and an efficient control of the phase is crucial for improving the performance and scalability. Furthermore, employing new methods to shift or control the phase may lead to the development of novel superconducting device applications, such as cryogenic memory and quantum computing devices. Recently, as a result of the progress in nanofabrication techniques, superconducting phase shifts utilizing π states have been realized. In this review, following a discussion of the basic physics of phase propagation and shifts in hybrid superconducting structures, interesting phenomena and device applications in phase-shifted superconducting systems are presented. In addition, various possibilities for developing electrically and magnetically controllable 0 and π junctions are presented; these possibilities are expected to be useful for future devices.

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Materials in superconducting quantum bits

Abstract: Abstract

Cited by 251 publications

References 87 publications

Evolution of Nanowire Transmon Qubits and Their Coherence in a Magnetic Field

Evolution of Nanowire Transmon Qubits and Their Coherence in a Magnetic Field

Thermal and Residual Excited-State Population in a 3D Transmon Qubit

Phase Shift and Control in Superconducting Hybrid Structures

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