Browsing by Author "Golubev, D. S."
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- Crossover between Electron-Phonon and Boundary-Resistance Limits to Thermal Relaxation in Copper Films
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2019-08-23) Wang, L. B.; Saira, O-P; Golubev, D. S.; Pekola, J. P.We observe a crossover fromelectron-phonon (e-ph) coupling limited energy relaxation to that governed by thermal boundary resistance (phonon-phonon coupling, ph-ph) in copper films at subkelvin temperatures. Our measurement yields a quantitative picture of heat currents, in terms of temperature dependences and magnitudes, in both e-ph and pp limited regimes, respectively. We show that by adding a third layer in between the copper film and the substrate, the thermal boundary resistance is increased fourfold, consistent with an assumed series connection of thermal resistances. - Dispersive Thermometry with a Josephson Junction Coupled to a Resonator
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2016-08-10) Saira, O. -P.; Zgirski, M.; Viisanen, K. L.; Golubev, D. S.; Pekola, J. P.We embed a small Josephson junction in a microwave resonator that allows simultaneous dc biasing and dispersive readout. Thermal fluctuations drive the junction into phase diffusion and induce a temperature-dependent shift in the resonance frequency. By sensing the thermal noise of a remote resistor in this manner, we demonstrate primary thermometry in the range of 300 mK to below 100 mK, and high-bandwidth (7.5 MHz) operation with a noise-equivalent temperature of better than 10 mu K/root Hz. At a finite bias voltage close to a Fiske resonance, amplification of the microwave probe signal is observed. We develop an accurate theoretical model of our device based on the theory of dynamical Coulomb blockade. - Lasing in circuit quantum electrodynamics with strong noise
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2015) Marthaler, M.; Utsumi, Y.; Golubev, D. S.We study a model which can describe a superconducting single-electron transistor or a double quantum dot coupled to a transmission-line oscillator. In both cases the degree of freedom is given by a charged particle, which couples strongly to the electromagnetic environment or phonons. We consider the case where a lasing condition is established and study the dependence of the average photon number in the resonator on the spectral function of the electromagnetic environment. We focus on three important cases: a strongly coupled environment with a small cutoff frequency, a structured environment peaked at a specific frequency, and 1/f noise. We find that the electromagnetic environment can have a substantial impact on the photon creation. Resonance peaks are in general broadened and additional resonances can appear. - Maxwell's demon based on a single qubit
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2016-01-05) Pekola, J. P.; Golubev, D. S.; Averin, D. V.We propose and analyze Maxwell's demon based on a single qubit with avoided level crossing. Its operation cycle consists of adiabatic drive to the point of minimum energy separation, measurement of the qubit state, and conditional feedback. We show that the heat extracted from the bath at temperature T can ideally approach the Landauer limit of k(B)T ln 2 per cycle even in the quantum regime. Practical demon efficiency is limited by the interplay of Landau-Zener transitions and coupling to the bath. We suggest that an experimental demonstration of the demon is fully feasible using one of the standard superconducting qubits. - Nonlocal thermoelectricity in a hybrid superconducting graphene device
A4 Artikkeli konferenssijulkaisussa(2021-06-16) Golubev, D. S.; Kirsanov, N. S.; Tan, Z. B.; Laitinen, A.; Galda, A.; Vinokur, V. M.; Haque, M.; Savin, A.; Lesovik, G. B.; Hakonen, P. J.The Seebeck effect producing voltage difference from temperature gradient has a wide spectrum of applications. Recent theoretical studies show that the Cooper pair splitting and the elastic co-tunneling can give rise to the nonlocal Seebeck effect in hybrid normal metal-superconductor-normal metal systems. Here we propose a coherent transport description of this nonlocal effect and validate its experimental observation in a graphene-based Cooper pair splitter. - Observation of the Bloch-Siegert shift in a driven quantum-to-classical transition
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2017-07-07) Pietikäinen, I.; Danilin, S.; Sampath Kumar, Karthikeyan; Vepsäläinen, A.; Golubev, D. S.; Tuorila, J.; Paraoanu, G. S.We show that the counter-rotating terms of the dispersive qubit-cavity Rabi model can produce relatively large and nonmonotonic Bloch-Siegert shifts in the cavity frequency as the system is driven through a quantum-to-classical transition. Using a weak microwave probe tone, we demonstrate experimentally this effect by monitoring the resonance frequency of a microwave cavity coupled to a transmon and driven by a microwave field with varying power. In the weakly driven regime (quantum phase), the Bloch-Siegert shift appears as a small constant frequency shift, while for a strong drive (classical phase) it presents an oscillatory behavior as a function of the number of photons in the cavity. The experimental results are in agreement with numerical simulations based on the quasienergy spectrum. - Photon blockade and the quantum-to-classical transition in the driven-dissipative Josephson pendulum coupled to a resonator
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2019-06-20) Pietikäinen, I.; Tuorila, J.; Golubev, D. S.; Paraoanu, G. S.We investigate the driven quantum phase transition between the oscillating motion and the classical nearly free rotations of the Josephson pendulum coupled to a harmonic oscillator in the presence of dissipation. We refer to this as the Josephson-Rabi model. This model describes the standard setup of circuit quantum electrodynamics, where typically a transmon device is embedded in a superconducting cavity. We find that by treating the system quantum mechanically this transition occurs at higher drive powers than expected from an all-classical treatment, which is a consequence of the quasiperiodicity originating in the discrete energy spectrum of the bound states. We calculate the photon number in the resonator and show that its dependence on the drive power is nonlinear. In addition, the resulting multiphoton blockade phenomenon is sensitive to the truncation of the number of states in the transmon, which limits the applicability of the standard Jaynes-Cummings model as an approximation for the pendulum-oscillator system. We calculate the nth-order correlation functions of the blockaded microwave photons and observe the differences between the rotating-wave approximation and the full multilevel Josephson-Rabi Hamiltonian with the counter-rotating terms included. Finally, we compare two different approaches to dissipation, namely the Floquet-Born-Markov and the Lindblad formalisms. - Thermoelectric current in a graphene Cooper pair splitter
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2021-12) Tan, Z. B.; Laitinen, A.; Kirsanov, N. S.; Galda, A.; Vinokur, V. M.; Haque, M.; Savin, A.; Golubev, D. S.; Lesovik, G. B.; Hakonen, P. J.Generation of electric voltage in a conductor by applying a temperature gradient is a fundamental phenomenon called the Seebeck effect. This effect and its inverse is widely exploited in diverse applications ranging from thermoelectric power generators to temperature sensing. Recently, a possibility of thermoelectricity arising from the interplay of the non-local Cooper pair splitting and the elastic co-tunneling in the hybrid normal metal-superconductor-normal metal structures was predicted. Here, we report the observation of the non-local Seebeck effect in a graphene-based Cooper pair splitting device comprising two quantum dots connected to an aluminum superconductor and present a theoretical description of this phenomenon. The observed non-local Seebeck effect offers an efficient tool for producing entangled electrons.