Non-invasive thermometer based on proximity superconductor for ultra-sensitive calorimetry

We present radio-frequency thermometry based on a tunnel junction between a superconductor and proximitized normal metal. It allows operation in a wide range of biasing conditions. We demonstrate that the standard finite-bias quasiparticle tunneling thermometer suffers from large dissipation and loss of sensitivity at low temperatures, whereas thermometry based on zero bias anomaly avoids both these problems. For these reasons the latter method is suitable down to lower temperatures, here to about 25 mK. Both thermometers are shown to measure the same local temperature of the electrons in the normal metal in the range of their applicability

Quantum trajectory analysis of single microwave photon detection by nanocalorimetry

We apply quantum trajectory techniques to analyze a realistic set-up of a superconducting qubit coupled to a heat bath formed by a resistor, a system that yields explicit expressions of the relevant transition rates to be used in the analysis. We discuss the main characteristics of the jump trajectories and relate them to the expected outcomes ("clicks") of a fluorescence measurement using the resistor as a nanocalorimeter. As the main practical outcome we present a model that predicts the time-domain response of a realistic calorimeter subject to single microwave photons, incorporating the intrinsic noise due to the fundamental thermal fluctuations of the absorber and finite bandwidth of a thermometer

Ultrasensitive Calorimetric Detection of Single Photons from Qubit Decay

We describe a qubit linearly coupled to a heat bath, either directly or via a cavity. The main focus of the paper is on calorimetric detection in a realistic circuit, specifically a solid-state qubit coupled to a resistor as an absorber. The bath in the model is formed of oscillators initially in the ground state with a distribution of energies and coupling strengths. A direct numerical solution of the Schrodinger equation for the full system including up to 106 oscillators in the bath verifies the expected decay process. We address quantitatively the question of separation of the qubit and bath by adding a cavity in between which by detuning allows one to adjust the decay rate into a convenient regime for detection purposes. Most importantly, we propose splitting a quantum to two uncoupled baths and performing a cross-correlation measurement of their temperatures. This technique enhances significantly the signal-to-noise ratio of the calorimeter.Peer reviewe

Speeding-up a quantum refrigerator via counter-diabatic driving

We study the application of a counter-diabatic driving (CD) technique to enhance the thermodynamic efficiency and power of a quantum Otto refrigerator based on a superconducting qubit coupled to two resonant circuits. Although the CD technique is originally designed to counteract non-adiabatic coherent excitations in isolated systems, we find that it also works effectively in the open system dynamics, improving the coherence-induced losses of efficiency and power. We compare the CD dynamics with its classical counterpart, and find a deviation that arises because the CD is designed to follow the energy eigenbasis of the original Hamiltonian, but the heat baths thermalize the system in a different basis. We also discuss possible experimental realizations of our model.Comment: 9 pages, 8 figure

The Rise of the "Other" and the Fall of the "Self": from Hegel to Derrida

Since time immemorial, due to its metaphysically grounded perspective, western philosophy has not been able to detach itself from the egoistic outlook, and thus, the interaction with the "other” had no role in this philosophy. The world has always been interpreted from the perspective of "self" ignoring the "other". Reviewing this mode of thought from Ancient Greece to Modern Age, one can reveal a kind of repression and forgetfulness of "alterity" and difference which Levinas has well highlighted in his philosophy. The very foundation of this egoism can be traced back to the Socratic slogan "know yourself”. In the same spirit, a kind of self-centered moral philosophy has been developed, the clear example of which is Kant's ethics. In line with Hegelian tradition of recognition, contemporary thinkers have redefined ethics and politics and acknowledged the constitutional dependence of the “self” on the "other." Based on the coordinates of their thought as well as the historical condition of their own time in the formation of subjectivity, these thinkers have criticized the neglect of the “other”. Hegel's role in underlining the importance of the vital status of the “other” is unique. Hegel bridges all post-Hegelian currents on the concept of “Other”. Then, in the present essay, we seek to show that since Hegel’s time up to Derrida, we have been witness to the rise of “Other” and the fall of “Self”

Low Temperature Characteristics of the Metal-Superconductor NIS Tunneling Thermometer

We discuss the temperature dependence of a common low temperature local thermometer, a tunnel junction between a superconductor and a normal metal (NIS junction). Towards the lowest temperatures its characteristics tend to saturate, which is usually attributed to selfheating effects. In this technical note, we reanalyze this saturation and show that the temperature independent subgap current of the junction alone explains in some cases the low temperature behavior quantitatively.Peer reviewe

Long-time relaxation of a finite spin bath linearly coupled to a qubit

We discuss the long-time relaxation of a qubit linearly coupled to a finite bath of $N$ spins (two-level systems, TLSs), with the interaction Hamiltonian in rotating wave approximation. We focus on the regime $N\gg 1$, assuming that the qubit-bath coupling is weak, that the range of spin frequencies is sufficiently broad, and that all the spins are initialized in the ground state. Despite the model being perfectly integrable, we make two interesting observations about the effective system relaxation. First, as one would expect, the qubit relaxes exponentially towards its zero-temperature state at a well characterized rate. Second, the bath spins, even when mutually coupled, do not relax towards a thermal distribution, but rather form a Lorentzian distribution peaked at the frequency of the initially excited qubit. This behavior is captured by an analytical approximation that makes use of the property $N\gg 1$ to treat the TLS frequencies as a continuum and is confirmed by our numerical simulations.Comment: Invited contribution to the Lindblad memorial volume, to be published in Open Systems and Information Dynamic

Influence of device non-uniformities on the accuracy of Coulomb blockade thermometry

We investigate temperature uncertainty of Coulomb blockade thermometer (CBT) arising from inevitable non-uniformities in tunnel junction arrays. The corrections are proportional to the junction resistance variance in the linear operation regime and this result holds approximately also beyond this originally studied high temperature range. We present both analytical and numerical results, and discuss briefly their implications on achievable uniformity based on state-of-the-art fabrication of sensors.Peer reviewe

Ultimate Accuracy of Frequency to Power Conversion by Single-Electron Injection

We analyze theoretically the properties of the recently introduced and experimentally demonstratedconverter of frequency to power. The system is composed of a hybrid single-electron box with normalisland and superconducting lead, and the detector of the energy flow using a thermometer on a normalmetal bolometer. Here, we consider its potential for metrology. The errors in power arise mainly frominaccuracy of injecting electrons at the precise energy equal to the energy gap of the superconductor. Wecalculate the main systematic error in the form of the excess average energy of the injected electrons and itscumulants, and that due to subgap leakage. We demonstrate by analytic and numerical calculations that thesystematic error in detection can, in principle, be made much smaller than the injection errors, which also,with proper choice of system parameters, can be very small,Peer reviewe