We demonstrate quantum limited electronic refrigeration of a metallic island in a low temperature micro-circuit. We show that matching the impedance of the circuit enables refrigeration at a distance, of about 50 um in our case, through superconducting leads with a cooling power determined by the quantum of thermal conductance. In a reference sample with a mismatched circuit this effect is absent. Our results are consistent with the concept of electromagnetic heat transport. We observe and analyze the crossover between electromagnetic and quasiparticle heat flux in a superconductor.
A three terminal nanoscale refrigeration concept based on a vibron-coupled quantum dot hybrid system coupled to two electronic reservoirs and a phonon bath is proposed and analyzed in detail. While investigating the non-trivial role of electron-phonon interactions, we show that, although they are well known to be detrimental from a general refrigeration perspective, can be engineered to favorably improve the trade-off between the cooling power (CP) and the coefficient-of-performance (COP). Furthermore, an additional improvement in the trade-off can be facilitated by applying a high electronic …
Refrigeration of a solid-state system with light has potential applications for cooling small-scale electronics and photonics. We show theoretically that two coupled semiconductor quantum wells are efficient cooling media for optical refrigeration because they support long-lived indirect electron-hole pairs. Thermal excitation of these pairs to distinct higher-energy states with faster radiative recombination allows an efficient escape channel to remove thermal energy from the system. This allows reaching much higher cooling efficiencies than with single quantum wells. From band-diagram calcul…
In classical thermodynamics the work cost of control can typically be neglected. On the contrary, in quantum thermodynamics the cost of control constitutes a fundamental contribution to the total work cost. Here, focusing on quantum refrigeration, we investigate how the level of control determines the fundamental limits to cooling and how much work is expended in the corresponding process. \jona{We compare two extremal levels of control. First coherent operations, where the entropy of the resource is left unchanged, and second incoherent operations, where only energy at maximum entropy (i.e. h…
We study geometric energy transport in a slowly driven single-level quantum dot weakly coupled to electronic contacts and with strong onsite interaction, which can be either repulsive or attractive. Exploiting a recently discovered fermionic duality for the evolution operator of the master equation, we provide compact and insightful analytic expressions of energy pumping curvatures for any pair of driving parameters. This enables us to systematically identify and explain the pumping mechanisms for different driving schemes, thereby also comparing energy and charge pumping. We determine the con…
Cooling quantum systems is arguably one of the most important thermodynamic tasks connected to modern quantum technologies and an interesting question from a foundational perspective. It is thus of no surprise that many different theoretical cooling schemes have been proposed, differing in the assumed control paradigm and complexity, and operating either in a single cycle or in steady state limits. Working out bounds on quantum cooling has since been a highly context dependent task with multiple answers, with no general result that holds independent of assumptions. In this letter we derive a u…
The Josephson effect is one of the most studied macroscopic quantum phenomena in condensed matter physics and has been an essential part of the quantum technologies development over the last decades. It is already used in many applications such as magnetometry, metrology, quantum computing, detectors or electronic refrigeration. However, developing devices in which the induced superconductivity can be monitored, both spatially and in its magnitude, remains a serious challenge. In this work, we have used local gates to control confinement, amplitude and density profile of the supercurrent induc…
Fragile quantum effects such as single electron charging in quantum dots or macroscopic coherent tunneling in superconducting junctions are the basis of modern quantum technologies. These phenomena can only be observed in devices where the characteristic spacing between energy levels exceeds the thermal energy, $k_\textrm{B}T$, demanding effective refrigeration techniques for nanoscale electronic devices. Commercially available dilution refrigerators have enabled typical electron temperatures in the $10$ to $100\,$mK regime, however indirect cooling of nanodevices becomes inefficient due to st…
An unconventional method of continuous solid-state cryogenic cooling utilizing the electron subband degeneracy of semiconductor heterostructures is proposed in this Letter. An electrostatic heat pump is modeled, which employs subband "expansion" and "compression" to reach sub-dilution refrigeration temperatures with the fundamental limit set by electron-phonon interaction. Using an ultra-wide GaAs quantum well as an example, the cooling power per unit volume is estimated to reach $4.5\ \rm mW/cm^3$ with a hot-side temperature of $300\ \rm mK$, suitable for applications such as quantum computer…
The energy efficiency and power of a quantum thermoelectric system with multiple electric currents and only one heat currents are studied. The system is connected to the hot heat bath with one terminal but the cold bath with multiple terminals or vice versal. We find that the cooperative effects can be a potentially useful tool in improving the energy efficiency and output power in multi-terminal mesoscopic thermoelectric systems. As an example, we show that the cooperation between the two thermoelectric effects in three-terminal thermoelectric systems leads to markedly improved performance of…
Quantum physics emerge and develop as temperature is reduced. Although mesoscopic electrical circuits constitute an outstanding platform to explore quantum behavior, the challenge in cooling the electrons impedes their potential. The strong coupling of such micrometer-scale devices with the measurement lines, combined with the weak coupling to the substrate, makes them extremely difficult to thermalize below 10 mK and imposes in-situ thermometers. Here we demonstrate electronic quantum transport at 6 mK in micrometer-scale mesoscopic circuits. The thermometry methods are established by the com…
Solid-state quantum emitters that couple coherent optical transitions to long-lived spin qubits are essential for quantum networks. Here we report on the spin and optical properties of individual tin-vacancy (SnV) centers in diamond nanostructures. Through cryogenic magneto-optical and spin spectroscopy, we verify the inversion-symmetric electronic structure of the SnV, identify spin-conserving and spin-flipping transitions, characterize transition linewidths, measure electron spin lifetimes and evaluate the spin dephasing time. We find that the optical transitions are consistent with the radi…
Motivated by the recent synthesis of two-dimensional monolayer AlSb, we theoretically investigate its ground state and electronic properties using the first-principles calculations coupled with Bethe-Salpeter equation. An excitonic instability is revealed as a result of larger exciton binding energy than the corresponding one-electron energy gap by $\sim$0.1 eV, which is an indicative of a many-body ground state accompanied by spontaneous exciton generation. Including the spin-orbit coupling is proven to be a must to correctly predict the ground state. At room temperature, the two-dimensional …
In the microscopic modeling of new-generation electronic quantum nanodevices a variety of simulation strategies have been proposed and employed. Aim of this Letter is to point out virtues versus intrinsic limitations of non-Markovian density-matrix approaches; we shall show that the usual mean-field treatment may lead to highly unphysical results, like negative distribution probabilities and non-dissipative behaviours, which are particularly severe in zero-dimensional electronic systems coupled to dispersionless phonon modes. This is in striking contrast with Markovian treatments, where a prop…
Electronic transport in BN-encasulated graphene limited by remote phonon scattering
Laboratoire Charles Coulomb (L2C), UMR 5221 CNRS-Université de Montpellier（蒙彼利埃大学查尔斯·库隆实验室）；Aix Marseille Univ, CNRS, CINaM, AMUTech（艾克斯马赛大学）；University of Modena and Reggio Emilia（摩德纳和雷焦艾米利亚大学）；Sapienza Università di Roma（罗马第一大学）
Quantum physics predicts that there is a fundamental maximum heat conductance across a single transport channel, and that this thermal conductance quantum $G_Q$ is universal, independent of the type of particles carrying the heat. Such universality, combined with the relationship between heat and information, signals a general limit on information transfer. We report on the quantitative measurement of the quantum limited heat flow for Fermi particles across a single electronic channel, using noise thermometry. The demonstrated agreement with the predicted $G_Q$ establishes experimentally this …
The development of spin qubits for quantum technologies requires their protection from the main source of finite-temperature decoherence: atomic vibrations. Here we eliminate one of the main barriers to the progress in this field by providing a complete first-principles picture of spin relaxation that includes up to two-phonon processes. Our method is based on machine learning and electronic structure theory and makes the prediction of spin lifetime in realistic systems feasible. We study a prototypical vanadium-based molecular qubit and reveal that the spin lifetime at high temperature is lim…
Electronic structure and transport characteristics of coupled CdS and ZnSe quantum dots are studied using density functional theory and non equilibrium Greens function method respectively. Our investigations show that in these novel coupled dots, the frontier occupied and unoccupied molecular orbitals are spatially located in two different parts of the coupled dot, thereby indicating the possibility of asymmetry in electronic transport. We have calculated electronic transport through the coupled quantum dot by varying the coupling strength between the individual quantum dots in the limits of w…
Open-system approaches are gaining traction in the simulation of charge transport in nanoscale and molecular electronic devices. In particular, "extended reservoir" simulations, where explicit reservoir degrees of freedom are present, allow for the computation of both real-time and steady-state properties but require relaxation of the extended reservoirs. The strength of this relaxation, $γ$, influences the conductance, giving rise to a "turnover" behavior analogous to Kramers' turnover in chemical reaction rates. We derive explicit, general expressions for the weak and strong relaxation limit…
