Tunable Coupling of Superconducting Qubits

Blais, Alexandre; Brink, Alec Maassen van den; Zagoskin, A. M.

doi:10.1103/physrevlett.90.127901

Cited by 188 publications

(169 citation statements)

References 24 publications

(46 reference statements)

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“…[12][13][14] With regard to using superconducting systems in quantum technologies, it has been shown that Josephson weak link circuits, and in particular SQUID rings in the quantum regime, are highly nonperturbative in nature and can generate very strong nonlinear interactions with classical circuit environments. [15][16][17][18] In this paper we provided a demonstration that this nonperturbative ͑nonlinear͒ behavior is crucial to the understanding of the interaction of SQUID rings with circuit environments. In this work we first consider the adiabatic ͑ground state͒ interaction of a quantum regime SQUID ring inductively coupled to a classical parallel resonance LC ͑tank͒ circuit.…”

Section: Introductionmentioning

confidence: 99%

Energy downconversion between classical electromagnetic fields via a quantum mechanical SQUID ring

et al. 2005

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We consider the interaction of a quantum mechanical SQUID ring with a classical resonator ͑a parallel LC tank circuit͒. In our model we assume that the evolution of the ring maintains its quantum mechanical nature, even though the circuit to which it is coupled is treated classically. We show that when the SQUID ring is driven by a classical monochromatic microwave source, energy can be transferred between this input and the tank circuit, even when the frequency ratio between them is very large. Essentially, these calculations deal with the coupling between a single macroscopic quantum object ͑the SQUID ring͒ and a classical circuit measurement device where due account is taken of the nonperturbative behavior of the ring and the concomitant nonlinear interaction of the ring with this device.

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Section: Introductionmentioning

confidence: 99%

Energy downconversion between classical electromagnetic fields via a quantum mechanical SQUID ring

et al. 2005

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“…Let δ = B z − ω be the detuning. If we let the PCB and the (initially un-excited) LC resonator interact right in resonance, i.e., |δ − 2γ| ≪ g ≪ ω or |δ + 2γ| ≪ g ≪ ω [23], state transfer occurs between the PCB and the LC resonator [13,14]. This is not allowed in our scheme, since it will drive the PCB out of the DFS.…”

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confidence: 99%

“…Schemes allowing to compute with invariable couplings were also studied [11,12]. Others have recently discussed to use an LC circuit to actively mediate the interaction between superconducting qubits [13,14].The requirement to reduce decoherence and the desire for the easiest manipulation apply to all QIP implementations. Unfortunately, it is not always easy to accomplish both -actually the goals are often contradictory -since reducing decoherence may require extra complication in the manipulation.…”

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confidence: 99%

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confidence: 99%

“…This is not allowed in our scheme, since it will drive the PCB out of the DFS. Besides, once the LC resonator is excited, we will have additional decoherence due to the finite quality of the LC resonator [13,14]. Therefore, we only work in the dispersive region, g ≪ |δ ± 2γ| ≪ ω.…”

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confidence: 99%

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Dispersive manipulation of paired superconducting qubits

et al. 2004

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We combine the ideas of qubit encoding and dispersive dynamics to enable robust and easy quantum information processing (QIP) on paired superconducting charge boxes sharing a common bias lead. We establish a decoherence free subspace on these and introduce universal gates by dispersive interaction with a LC resonator and inductive couplings between the encoded qubits. These gates preserve the code space and only require the established local symmetry and the control of the voltage bias.PACS numbers: 03.67. Lx, 74.50.+r Superconducting nano-circuits consisting of charge boxes (CB) [1] are among the most promising candidates for a quantum computer. Coherent control of a single charge qubit [2], long decoherence time [3] and, more recently, coupled two qubit systems [4] have been demonstrated. But despite this encouraging experimental progress, there are serious difficulties with superconducting QIP which may appear insurmountable. The first is the severe decoherence experienced by these macroscopic qubits, which are coupled to a large number of degrees of freedom in their environment including control circuitry [5]. A few methods have been employed to reduce the decoherence [6,7], but they usually require sophisticated manipulation or significant overhead in the control circuitry. The second major difficulty comes from the imperfect control realizable in solid state systems. Specifically, one finds it difficult to achieve controllable couplings between superconducting qubits, since the commonly used hard-wired inductive or capacitive couplings are untunable. Great effort has been exercised to realize controllable couplings [8,9,10]. Schemes allowing to compute with invariable couplings were also studied [11,12]. Others have recently discussed to use an LC circuit to actively mediate the interaction between superconducting qubits [13,14].The requirement to reduce decoherence and the desire for the easiest manipulation apply to all QIP implementations. Unfortunately, it is not always easy to accomplish both -actually the goals are often contradictory -since reducing decoherence may require extra complication in the manipulation.In this work we show how to achieve both goals. Using a closely placed pair of charge boxes (PCB) sharing a common bias lead as the logic qubit, we can encode information in a fashion immune to collective noise, which is the dominating decoherence source in our setting. We introduce LC resonators inductively coupled to the PCBs whose virtual excitations allow us to manipulate the PCB dispersively; all interactions will be off resonance, without energy transfer [15,16], and thus a logical qubit stays within its encoding space even during manipulation. By inductively coupling the * Electronic address: mikewulf@pas.rochester.edu CBs and taking advantage of dispersive dynamics again, controlled phases can be induced between logical qubits.Combining dispersive dynamics and encoding offers a new method for QIP. It overcomes the major difficulties of superconducting CBs in a realistic and very si...

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Implementing Qubits with Superconducting Integrated Circuits

Devoret

Martinis

Experimental Aspects of Quantum Computing

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Tunable Coupling of Superconducting Qubits

Cited by 188 publications

References 24 publications

Energy downconversion between classical electromagnetic fields via a quantum mechanical SQUID ring

Energy downconversion between classical electromagnetic fields via a quantum mechanical SQUID ring

Dispersive manipulation of paired superconducting qubits

Implementing Qubits with Superconducting Integrated Circuits

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