Dynamic features of a charge qubit closed by a superconducting inductive ring

Krech, W.; Grajcar, M.; Born, D.; Zhilyaev, I. N.; Wagner, Th.; Il’ichev, É. A.; Greenberg, Ya. S.

doi:10.1016/s0375-9601(02)01315-4

Cited by 17 publications

(26 citation statements)

References 14 publications

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“…In the quantum case the current is equal to the expectation value of the current operator: I = I . For our system we have 6,9 : I = −I 0 σ z , where the ground state current is…”

Section: B Qubit-tank Circuit Arrangementmentioning

confidence: 99%

“…For instance a charge qubit can be a conventional single-Cooper-pair transistor closed by a superconducting loop 8 . For a certain range of the relationship between effective Josephson coupling and charge energies ε J /E C of the transistor's junctions, this device is effectively a two-level quantum system with externally controlled parameters 6,8,9,10 . Moreover, similar to both the traditional nonhysteretic RF SQUID 11,12 and the DC SQUID 13 , the phase-biased transistor coupled to a highquality radio-frequency tank circuit 14 turns out to be an ideal parametric converter of charge and flux signals with standard quantum limit of the energy resolution.…”

Section: Introductionmentioning

confidence: 99%

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Multiphoton transitions between energy levels in a phase-biased Cooper-pair box

Шнырков

Wagner²,

Born

et al. 2006

Phys. Rev. B

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We investigated both theoretically and experimentally dynamic features of a phase-biased charge qubit consisting of a single-Cooper-pair transistor closed by a superconducting loop. The effective inductance of the qubit was probed by a high-quality tank circuit. In the presence of a microwave power, with a frequency of the order of the qubit energy level separation, an alteration of the qubit inductance was observed. We demonstrate that this effect is caused by the redistribution of the qubit level population. The excitation of the qubit by one-, two-, and three-photon processes was detected. Quantitative agreement between theory and experimental data was found.

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“…In the quantum case the current is equal to the expectation value of the current operator: I = I . For our system we have 6,9 : I = −I 0 σ z , where the ground state current is…”

Section: B Qubit-tank Circuit Arrangementmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Multiphoton transitions between energy levels in a phase-biased Cooper-pair box

Шнырков

Wagner²,

Born

et al. 2006

Phys. Rev. B

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“…Here the domination of the Coulomb energy of a Cooper pair 4E C over the coupling energy ε J is assumed, 4E C /ε J > 1. The eigenstates, {|− , |+ }, of this Hamiltonian are discriminated by the direction of the supercurrent in the ring 21 .…”

Section: Multiphoton Excitations In the Interferometer-type Chargmentioning

confidence: 99%

“…First, it is convenient to describe Rabi oscillations and multiphoton transitions. Second, in the case of the charge qubit these states {|− , |+ } are eigenstates of the current operator, which is related to the experimentally measurable values 21 . The important point is that we can get the occupation probability of any state provided we know the probabilities for the states in a particular basis.…”

Section: Introductionmentioning

confidence: 99%

Dynamic behavior of Josephson-junction qubits: crossover between Rabi oscillations and Landau–Zener transitions

Shevchenko

Kiyko

Omelyanchouk

et al. 2005

Low Temperature Physics

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We study the dynamic behaviour of a quantum two-level system with periodically varying parameters by solving the master equation for the density matrix. Two limiting cases are considered: multiphoton Rabi oscillations and Landau-Zener (LZ) transitions. The approach is applied to the description of the dynamics of superconducting qubits. In particular, the case of the interferometertype charge qubit with periodically varying parameters (gate voltage or magnetic flux) is investigated. The time-averaged energy level populations are calculated as functions of the qubit's control parameters.

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“…In the so-called magic points (extremum or saddle points), i.e., A (Q 0 = 0, φ = π), B (Q 0 = 0, φ = 0) and C (Q 0 = e, φ = 0), the absolute values of L −1 0,1 achieve local maxima, while in the avoided level-crossing point D (Q 0 = e, φ = π) its value is the largest [8]. Specifically, in point D, where effective coupling is small, E J (π) = |E J1 − E J2 | ≪ E c , these values for two states are equal to [9] …”

Section: Qubit Parameters and The Modelmentioning

confidence: 95%

Coupling and Dephasing in Josephson Charge-Phase Qubit with Radio Frequency Readout

Zorin

Quantum Computing in Solid State Systems

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The Cooper pair box qubit of a two-junction-SQUID configuration enables the readout of the qubit states by probing the effective Josephson inductance of the SQUID. This is realized by coupling the qubit to a high-Q tank circuit which induces a small alternating supercurrent in the SQUID loop. The effect of a small (but finite) geometrical inductance of the loop on the eigenstates of the system is figured out. The effect of qubit dephasing due to quadratic coupling to the tank circuit is evaluated. It is shown that the rate of dephasing in the vicinity of the magic points is relatively low unless the Josephson junctions forming the qubit are rather dissimilar. In the vicinity of the avoided level-crossing point such dephasing is always significant.

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Dynamic features of a charge qubit closed by a superconducting inductive ring

Cited by 17 publications

References 14 publications

Multiphoton transitions between energy levels in a phase-biased Cooper-pair box

Multiphoton transitions between energy levels in a phase-biased Cooper-pair box

Dynamic behavior of Josephson-junction qubits: crossover between Rabi oscillations and Landau–Zener transitions

Coupling and Dephasing in Josephson Charge-Phase Qubit with Radio Frequency Readout

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