Coherence and Decay of Higher Energy Levels of a Superconducting Transmon Qubit

Peterer, Michael; Bader, Samuel James; Jin, Xiaoyue; Yan, Fei; Kamal, Archana; Gudmundsen, Theodore; Leek, Peter; Orlando, Terry P.; Oliver, William; Gustavsson, Simon

doi:10.1103/physrevlett.114.010501

Cited by 188 publications

(162 citation statements)

References 32 publications

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“…Taking Δ ¼ 170 μeV, R N ¼ 9.5 kΩ and C ¼ 80 fF [52,56] wet (Oxford Kelvinox 400) refrigerator with similar wiring and filtering configurations [52]. In particular, we observed T ¼ 35 AE 4 mK for a capacitively shunted flux qubit with similar qubit parameters, including f ge ¼ 4.7 GHz, f resonator ¼ 8.3 GHz, Q c ¼ 5000 and g=2π ¼ 100 MHz.…”

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confidence: 74%

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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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confidence: 74%

“…1(a), the readout-signal amplitude as a function of readout-signal frequency indicates the dressed cavity frequency for states jgi, jei, and jfi. For purposes of illustration, the qubit was prepared in state jfi using sequential π g→e and π e→f pulses, and then allowed to relax and partially populate states jgi and jei before readout [56].…”

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confidence: 99%

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

et al. 2015

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“…The parameters used in the numerical simulation are: (i) ∆ a /2π = 1.5 GHz, ∆/2π = 1.25 GHz; (ii) δ b /2π = 0.25 GHz; (iii) γ Here we consider a rather conservative case for both the inter-resonator crosstalk and the decoherence time of flux qudits because the interresonator crosstalk strength can be smaller by at least one order of magnitude [29] and decoherence time ranging from 70 µs to 1 ms has been reported for a superconducting qudit [60][61][62][63]. …”

Section: Master Equation and Parameters Used In Numerical Simulationmentioning

confidence: 99%

Entangling two oscillators with arbitrary asymmetric initial states

Yang

Zheng

et al. 2017

Phys. Rev. A

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We present a Hamiltonian, which can be used to convert any asymmetric state |ϕ a|φ b of two oscillators a and b into an entangled state via a single-step operation. Furthermore, with this Hamiltonian and local operations only, two oscillators, initially in any asymmetric initial states, can be entangled with a third oscillator. The prepared entangled states can be engineered with an arbitrary degree of entanglement. A discussion on the realization of this Hamiltonian is given. Numerical simulations show that, with current circuit QED technology, it is feasible to generate highfidelity entangled states of two microwave optical fields, such as entangled coherent states, entangled squeezed states, entangled coherent-squeezed states, and entangled cat states. Our finding opens a new avenue for creating not only wave-like or particle-like entanglement but also novel wave-like and particle-like hybrid entanglement.PACS numbers: 03.67. Bg, 42.50.Dv, 85.25.Cp Introduction. Entangled states of light are a fundamental resource for many quantum information tasks [1][2][3][4][5][6][7][8]. In the regime of discrete variables, entanglement of up to eight photons has been experimentally demonstrated via linear optical devices [9,10]. In the regime of continuous variables, EPR states of light have been experimentally generated from two independent squeezed fields [11,12], two independent coherent fields [13], or a single squeezed light source [14]; two-or three-color entangled states of light have been experimentally prepared by means of non-degenerate optical parametric oscillators [15][16][17]. Recently, hybrid entanglement between particlelike and wave-like optical qubits or between quantum and classical states of light [18,19] has also been demonstrated in experiments, which has drawn increasing attention because hybrid entanglement of light is a key resource in establishing hybrid quantum networks and connecting quantum processors with different encoding qubits. Moreover, a large number of theoretical proposals have been presented for generating particular types of entangled states of light or photons in various physical systems [20][21][22][23][24][25][26][27][28][29][30][31][32][33].In this paper, we propose a Hamiltonian, which can be used to convert any asymmetric state |ϕ a |φ b of two oscillators a and b into an entangled state α |ϕ a |φ b ± β |φ a |ϕ b . Here the term asymmetric state refers to the product state |ϕ a |φ b , with |ϕ = |φ . The procedure consists of a single unitary operation and a posterior measurement on the states of the qudit coupler that is used to couple the oscillators. Furthermore, by combining this Hamiltonian with additional local operations, two oscillators a and b initially in any asymmetric state |ϕ a |φ b and a third oscillator in the vacuum

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“…The energy levels of a transmon qubit [31] are in a ladder shape, and the anharmonicity is small, which limits the coupling strength between neighboring levels to the order of 10 * zyxue@scnu.edu.cn MHz in order to individually address the interactions [28,32]. Therefore, even with newly demonstrated good coherent times of multilevels in the transmon qubit [32], the implementation of a nontrivial two-qubit holonomic gate, which needs much more complicated cavity-induced interaction between two three-level systems [26], is still very challenging. Alternatively, there are schemes using circuits more complicated than transmons to mimic a multilevel system [7,16,20].…”

Section: Introductionmentioning

confidence: 99%

Universal holonomic quantum gates in decoherence-free subspace on superconducting circuits

2015

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To implement a set of universal quantum logic gates based on non-Abelian geometric phases, it is a conventional wisdom that quantum systems beyond two levels are required, which is extremely difficult to fulfill for superconducting qubits and appears to be a main reason why only single-qubit gates were implemented in a recent experiment [A. A. Abdumalikov Jr. et al., Nature (London) 496, 482 (2013)]. Here we propose to realize nonadiabatic holonomic quantum computation in decoherence-free subspace on circuit QED, where one can use only the two levels in transmon qubits, a usual interaction, and a minimal resource for the decoherence-free subspace encoding. In particular, our scheme not only overcomes the difficulties encountered in previous studies, but also can still achieve considerably large effective coupling strength, such that high fidelity quantum gates can be achieved. Therefore, the present scheme makes realizing robust holonomic quantum computation with superconducting circuits very promising.

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Coherence and Decay of Higher Energy Levels of a Superconducting Transmon Qubit

Cited by 188 publications

References 32 publications

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

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

Entangling two oscillators with arbitrary asymmetric initial states

Universal holonomic quantum gates in decoherence-free subspace on superconducting circuits

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