Quantum-circuit refrigerator

Tan, Kuan Yen; Partanen, Matti; Lake, Russell; Govenius, Joonas; Masuda, S.; Möttönen, Mikko

doi:10.1038/ncomms15189

Cited by 118 publications

(151 citation statements)

References 45 publications

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“…This model accurately describes the physics of the quantum-circuit refrigerator and the cryogenic microwave source demonstrated in Refs. [40,41]. In contrast to the previous model [40,41], we are able to capture fine details of the physical circuit, multiphoton states, and multiphoton absorption.…”

Section: Introductionmentioning

confidence: 97%

“…Although the early work on photon-assisted tunneling at NIS junctions focused on the effect of the electromagnetic circuit on the tunnel current [19][20][21]32,33], recent studies also demonstrate the effect of the tunneling events on the state of the circuit [34][35][36][37][38][39][40][41][42][43]. Importantly, a quantum-circuit refrigerator and cryogenic microwave source based on photonassisted tunneling of electrons through NIS junctions were demonstrated in Refs.…”

Section: Introductionmentioning

confidence: 99%

“…Importantly, a quantum-circuit refrigerator and cryogenic microwave source based on photonassisted tunneling of electrons through NIS junctions were demonstrated in Refs. [40,41], see schematic in Fig. 1.…”

Section: Introductionmentioning

confidence: 99%

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Theory of quantum-circuit refrigeration by photon-assisted electron tunneling

et al. 2017

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We focus on a recently experimentally realized scenario of normal-metal-insulator-superconductor tunnel junctions coupled to a superconducting resonator. We develop a first-principles theory to describe the effect of photon-assisted electron tunneling on the quantum state of the resonator. Our results are in very good quantitative agreement with the previous experiments on refrigeration and heating of the resonator using the photon-assisted tunneling, thus providing a stringent verification of the developed theory. Importantly, our results provide simple analytical estimates of the voltage-tunable coupling strength and temperature of the thermal reservoir formed by the photon-assisted tunneling. Consequently, they are used to introduce optimization principles for initialization of quantum devices using such a quantum-circuit refrigerator. Thanks to the first-principles nature of our approach, extension of the theory to the full spectrum of quantum electric devices seems plausible.

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Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Theory of quantum-circuit refrigeration by photon-assisted electron tunneling

et al. 2017

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“…23,24 If the bath has a lower effective temperature than the qubit, the ground-state fidelity of the qubit is increased. This type of set-up is a part of environmental quantum-state engineering by dissipation, where one aims to drive the system into a desired steady state by using a carefully tailored environment.…”

Section: Introductionmentioning

confidence: 99%

Efficient protocol for qubit initialization with a tunable environment

et al. 2017

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We propose an efficient qubit initialization protocol based on a dissipative environment that can be dynamically adjusted. Here, the qubit is coupled to a thermal bath through a tunable harmonic oscillator. On-demand initialization is achieved by sweeping the oscillator rapidly into resonance with the qubit. This resonant coupling with the engineered environment induces fast relaxation to the ground state of the system, and a consecutive rapid sweep back to off resonance guarantees weak excess dissipation during quantum computations. We solve the corresponding quantum dynamics using a Markovian master equation for the reduced density operator of the qubit-bath system. This allows us to optimize the parameters and the initialization protocol for the qubit. Our analytical calculations show that the ground-state occupation of our system is well protected during the fast sweeps of the environmental coupling and, consequently, we obtain an estimate for the duration of our protocol by solving the transition rates between the low-energy eigenstates with the Jacobian diagonalization method. Our results suggest that the current experimental state of the art for the initialization speed of superconducting qubits at a given fidelity can be considerably improved.

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“…Mesoscopic refrigerators based on this effect make use of semiconductor quantum dots 7,8 , superconducting-insulator-normal metal (SIN) junctions 9-12 , or single-electron transistors (SET) 13,14 . Cooling mediated by the coupling to cavity photons has also been proposed in Josephson junctions 15-17 and implemented for the refrigeration of metallic islands [18][19][20][21][22] . Here an alternative approach is proposed based on the capacitive coupling of a two-terminal SINIS SET to the system to be cooled, see Fig.…”

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confidence: 99%

Correlation-induced refrigeration with superconducting single-electron transistors

Sánchez

2017

Applied Physics Letters

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A model of a superconducting tunnel junction which refrigerates a nearby metallic island without any particle exchange is presented. Heat extraction is mediated by charge fluctuations in the coupling capacitance of the two systems. The interplay of Coulomb interaction and the superconducting gap reduces the power consumption of the refrigerator. The island is predicted to be cooled from lattice temperatures of 200 mK down to close to 50 mK, for realistic parameters. The results emphasize the role of non-equilibrium correlations in bipartite mesoscopic conductors. This mechanism can be applied to create local temperature gradients in tunnel junction arrays or explore the role of interactions in the thermalization of non-equilibrium systems.Quantum coherent processes relevant to quantum information or quantum thermodynamics 1 are usually damaged by temperature. Solid state quantum simulators 2 or heat engines 3,4 have recently been proposed that operate at very low temperatures. Finding ways to cool nanoscale systems 5,6 , or introduce local temperature gradients well below 100 mK without injecting charge into them is hence a demanding task. This way they are minimally perturbed and not affected by Joule heating.Thermoelectric refrigeration is traditionally based on the Peltier effect. Driving a current through a conductor with broken electron-hole symmetry converts thermal excitations into transport. Mesoscopic refrigerators based on this effect make use of semiconductor quantum dots 7,8 , superconducting-insulator-normal metal (SIN) junctions 9-12 , or single-electron transistors (SET) 13,14 . Cooling mediated by the coupling to cavity photons has also been proposed in Josephson junctions 15-17 and implemented for the refrigeration of metallic islands [18][19][20][21][22] . Here an alternative approach is proposed based on the capacitive coupling of a two-terminal SINIS SET to the system to be cooled, see Fig. 1. We consider cooling of a single-electron box (SEB) 23,24 : a Coulomb blockade island which exchanges electrons with a third terminal. The extraction of energy is mediated by the Coulomb repulsion of electrons in different islands, J. The superconducting gap, ∆, acts as an energy filter: At subgap voltages, only transitions that take energy from from the capacitor contribute to transport. A normal metal SET would unavoidably emit Joule heat at all voltages into the island. The manipulation of electrical and thermal flows in capacitively coupled normal metal or semiconductor systems has been recently demonstrated, including effects such as quantum dot heat engines 25-32 , autonomous Maxwell's demon operations 33,34 , thermal rectifiers 35-37 , memristors 38 , or single-electron current switches 39-41 . The interplay of the two relevant energy scales, J and ∆, in the cooling mechanism is investigated. Subgap transport in the SET is assisted by the Coulomb interaction, hence increasing the voltage window where cooling takes place. Hot electrons in the SET island are thus pumped over the gap of the supercond...

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Quantum-circuit refrigerator

Cited by 118 publications

References 45 publications

Theory of quantum-circuit refrigeration by photon-assisted electron tunneling

Theory of quantum-circuit refrigeration by photon-assisted electron tunneling

Efficient protocol for qubit initialization with a tunable environment

Correlation-induced refrigeration with superconducting single-electron transistors

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