Double SQUID tunable flux qubit manipulated by fast pulses: operation requirements, dissipation and decoherence

Chiarello, F.

doi:10.1140/epjb/e2007-00035-5

Cited by 12 publications

(14 citation statements)

References 29 publications

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“…The potential has been used to implement an Otto cycle, enabled by energy quantization and operating by adiabatic insertion and removal of the barrier. A possible candidate to realize our model of the quantum Stirling engine involves superconducting flux qubits where the symmetric potential can be controlled at very low temperatures [46,47] with well defined heat baths and the possibility of measurement of heat power [48].…”

Section: Discussionmentioning

confidence: 99%

Quantum heat engine based on level degeneracy

2019

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We study a quantum Stirling cycle which extracts work using quantized energy levels of a potential well. The work and the efficiency of the engine depend on the length of the potential well, and the Carnot efficiency is approached in a low temperature limiting case. We show that the lack of information about the position of the particle inside the potential well can be converted into useful work without resorting to any measurement. In the low temperature limit, we calculate the amount of work extractable from distinguishable particles, fermions, and bosons.

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Section: Discussionmentioning

confidence: 99%

Quantum heat engine based on level degeneracy

2019

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“…The device we consider is the so-called double SQUID [31], consisting of a superconducting loop of inductance L interrupted by a dc SQUID, a second smaller superconducting loop of inductance l interrupted by two identical Josephson junctions, each of (nominally) identical critical current i 0 and capacitance c [ Fig. 1(a) , being 0 = h/2e the flux quantum), which is controlled by a magnetic flux c applied to the small loop (this approximation holds if the loop is small enough, i.e., for li 0 0 ).…”

Section: Double Squidmentioning

confidence: 99%

Resonant effects in a SQUID qubit subjected to nonadiabatic changes

et al. 2014

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By quickly modifying the shape of the effective potential of a double SQUID flux qubit from a single-well to a double-well condition, we experimentally observe an anomalous behavior, namely, an alternation of resonance peaks, in the probability to find the qubit in a given flux state. The occurrence of Landau-Zener transitions as well as resonant tunneling between degenerate levels in the two wells may be invoked to partially justify the experimental results. A quantum simulation of the time evolution of the system indeed suggests that the observed anomalous behavior can be imputable to quantum coherence effects. The interplay among all these mechanisms has a practical implication for quantum computing purposes, giving a direct measurement of the limits on the sweeping rates possible for a correct manipulation of the qubit state by means of fast flux pulses, avoiding transitions to noncomputational states.

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“…In our case it is E C / h = 0.22 GHz, E L / h = 1920 GHz and E J / h = 7940 GHz leading to β 0 = 4.1. Depending on the value of β(ϕ c ), the potential U (ϕ) has a single-well or a double-well shape, with ϕ c controlling the barrier height in the double well (figure 1(b)) and the concavity in the single-well case (figures 1(c) and (d)), and ϕ x controlling the potential symmetry (figure 1(e)) [23,24]. The described potential presents a periodic behaviour in x and c [20].…”

Section: The Double Squid Qubit Manipulated By Fast Pulsesmentioning

confidence: 99%

“…The energy gaphε = E L ϕ ϕ x between them is almost constant in a large range of values of β(ϕ c ) because of the weak dependence of ϕ on β(ϕ c ). Approximate analytical expressions for the important quantities related to this case have been reported in [24].…”

Section: The Double Squid Qubit Manipulated By Fast Pulsesmentioning

confidence: 99%

Superconducting qubit manipulated by fast pulses: experimental observation of distinct decoherence regimes

et al. 2012

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A particular superconducting quantum interference device (SQUID) qubit, namely the double SQUID qubit, can be manipulated by rapidly modifying its potential with the application of fast flux pulses. In this system we observe coherent oscillations exhibiting non-exponential decay, indicating an unconventional decoherence mechanism. Moreover, via tuning the qubit in different conditions (different oscillation frequencies) by changing the pulse height, we observe a crossover between two distinct decoherence regimes and the existence of an 'optimal' point where the qubit is only weakly sensitive to intrinsic noise. We find that this behavior is in agreement with a model considering the decoherence caused essentially by low-frequency noise contributions, and we discuss the experimental results and possible issues.

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Double SQUID tunable flux qubit manipulated by fast pulses: operation requirements, dissipation and decoherence

Cited by 12 publications

References 29 publications

Quantum heat engine based on level degeneracy

Quantum heat engine based on level degeneracy

Resonant effects in a SQUID qubit subjected to nonadiabatic changes

Superconducting qubit manipulated by fast pulses: experimental observation of distinct decoherence regimes

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