Proposal for non-local electron-hole turnstile in the Quantum Hall regime

We present a theory for a mesoscopic turnstile that produces spatially separated streams of electrons and holes along edge states in the quantum Hall regime. For a broad range of frequencies in the non-adiabatic regime the turnstile operation is found to be ideal, producing one electron and one hole per cycle. The accuracy of the turnstile operation is characterized by the fluctuations of the transferred charge per cycle. The fluctuations are found to be negligibly small in the ideal regime.Comment: 4+ pages, 2 figure

Sub Decoherence Time Generation and Detection of Orbital Entanglement

Recent experiments have demonstrated sub decoherence time control of individual single-electron orbital qubits. Here we propose a quantum dot based scheme for generation and detection of pairs of orbitally entangled electrons on a timescale much shorter than the decoherence time. The electrons are entangled, via two-particle interference, and transferred to the detectors during a single cotunneling event, making the scheme insensitive to charge noise. For sufficiently long detector dot lifetimes, cross-correlation detection of the dot charges can be performed with real-time counting techniques, opening up for an unambiguous short-time Bell inequality test of orbital entanglement.Comment: 5 pages, 2 figures, 3 pages supplemental materia

Quantum heat fluctuations of single particle sources

Optimal single electron sources emit regular streams of particles, displaying no low frequency charge current noise. Due to the wavepacket nature of the emitted particles, the energy is however fluctuating, giving rise to heat current noise. We investigate theoretically this quantum source of heat noise for an emitter coupled to an electronic probe in the hot-electron regime. The distribution of temperature and potential fluctuations induced in the probe is shown to provide direct information on the single particle wavefunction properties and display strong non-classical features.Comment: 5 pages, 2 figure

Nanoscale Quantum Calorimetry with Electronic Temperature Fluctuations

Motivated by the recent development of fast and ultra-sensitive thermometry in nanoscale systems, we investigate quantum calorimetric detection of individual heat pulses in the sub-meV energy range. We propose a hybrid superconducting injector-calorimeter set-up, with the energy of injected pulses carried by tunneling electrons. Treating all heat transfer events microscopically, we analyse the statistics of the calorimeter temperature fluctuations and derive conditions for an accurate measurement of the heat pulse energies. Our results pave the way for novel, fundamental quantum thermodynamics experiments, including calorimetric detection of single microwave photons.Comment: 6 pages, 3 figures plus supplemental material, 8 pages, 1 figur

Experimental verification of reciprocity relations in quantum thermoelectric transport

Symmetry relations are manifestations of fundamental principles and constitute cornerstones of modern physics. An example are the Onsager relations between coefficients connecting thermodynamic fluxes and forces, central to transport theory and experiments. Initially formulated for classical systems, these reciprocity relations are also fulfilled in quantum conductors. Surprisingly, novel relations have been predicted specifically for thermoelectric transport. However, whereas these thermoelectric reciprocity relations have to date not been verified, they have been predicted to be sensitive to inelastic scattering, always present at finite temperature. The question whether the relations exist in practice is important for thermoelectricity: whereas their existence may simplify the theory of complex thermoelectric materials, their absence has been shown to enable, in principle, higher thermoelectric energy conversion efficiency for a given material quality. Here we experimentally verify the thermoelectric reciprocity relations in a four-terminal mesoscopic device where each terminal can be electrically and thermally biased, individually. The linear response thermoelectric coefficients are found to be symmetric under simultaneous reversal of magnetic field and exchange of injection and emission contacts. Intriguingly, we also observe the breakdown of the reciprocity relations as a function of increasing thermal bias. Our measurements thus clearly establish the existence of the thermoelectric reciprocity relations, as well as the possibility to control their breakdown with the potential to enhance thermoelectric performanceComment: 7 pages, 5 figure

Spectral distribution and wavefunction of electrons emitted from a single particle source in the quantum Hall regime

We investigate theoretically a scheme for spectroscopy of electrons emitted by an on-demand single particle source. The total system, with an electron turnstile source and a single level quantum dot spectrometer, is implemented with edge states in a conductor in the quantum Hall regime. Employing a Floquet scattering approach, the source and the spectrometer are analyzed within a single theoretical framework. The non-equilibrium distribution of the emitted electrons is analyzed via the direct current at the dot spectrometer. In the adiabatic and intermediate source frequency regimes, the distribution is found to be strongly peaked around the active resonant level of the turnstile. At high frequencies the distribution is split up into a set of fringes, resulting from the interplay of resonant transport through the turnstile and absorption or emission of individual Floquet quanta. For ideal source operation, with exactly one electron emitted per cycle, an expression for the single electron wavefunction is derived.Comment: 12 pages, 7 figure

Noise and Full Counting Statistics of Incoherent Multiple Andreev Reflection

We present a general theory for the full counting statistics of multiple Andreev reflections in incoherent superconducting-normal-superconducting contacts. The theory, based on a stochastic path integral approach, is applied to a superconductor-double barrier system. It is found that all cumulants of the current show a pronounced subharmonic gap structure at voltages $V=2\Delta/en$. For low voltages $V\ll\Delta/e$, the counting statistics results from diffusion of multiple charges in energy space, giving the $p$th cumulant $\propto V^{2-p}$, diverging for $p\geq 3$. We show that this low-voltage result holds for a large class of incoherent superconducting-normal-superconducting contacts.Comment: 4 pages, 4 figure

Charge qubit entanglement in double quantum dots

We study entanglement of charge qubits in a vertical tunnel-coupled double quantum dot containing two interacting electrons. Exact diagonalization is used to compute the negativity characterizing entanglement. We find that entanglement can be efficiently generated and controlled by sidegate voltages, and describe how it can be detected. For large enough tunnel coupling, the negativity shows a pronounced maximum at an intermediate interaction strength within the Wigner molecule regime.Comment: revised version of the manuscript, as published in EPL, 7 pages, 4 figure

Clauser-Horne inequality for electron counting statistics in multiterminal mesoscopic conductors

In this paper we derive the Clauser-Horne (CH) inequality for the full electron counting statistics in a mesoscopic multiterminal conductor and we discuss its properties. We first consider the idealized situation in which a flux of entangled electrons is generated by an entangler. Given a certain average number of incoming entangled electrons, the CH inequality can be evaluated for different numbers of transmitted particles. Strong violations occur when the number of transmitted charges on the two terminals is the same ($Q_1=Q_2$), whereas no violation is found for $Q_1\ne Q_2$. We then consider two actual setups that can be realized experimentally. The first one consists of a three terminal normal beam splitter and the second one of a hybrid superconducting structure. Interestingly, we find that the CH inequality is violated for the three terminal normal device. The maximum violation scales as 1/M and $1/M^2$ for the entangler and normal beam splitter, respectively, 2$M$ being the average number of injected electrons. As expected, we find full violation of the CH inequality in the case of the superconducting system.Comment: 26 pages, 9 figures. Ref. adde