Weak measurements of quantum effects in electronic nano-devices
Final Report Abstract
The project dealt with weak measurements of quantum effects in electronic nanostructures, addressing different facets and considering different possible setups. More specifically, as originally aimed, the project shed light on genuine quantum processes inaccessible to strong measurements by considering four representative cases. The detection of cotunneling of electrons and the corresponding time has been successfully described in two publications focusing on different regimes and ranging from purely theoretical analysis to realistic models for experiments. The main result is that a direct protocol to measure the cotunneling time can lead to time that deviate both from the expectation of classical intuition (though expected) and (more surprisingly) from an estimation via a quantum mechanical energy-time uncertainty principle: The weakly measured cotunneling time can be parametrically smaller than the naively estimated one in 2 dimensional diffusive dots. Two of the initially planned objectives (weak detection of adiabatic passage and of Majorana end states) were strategically shifted to more timely/deliverable ones. They lead to the proposal of weak-measurement based feedback for stabilizing the steady state entanglement from parity measurements and to the determination of the effects of interactions on quantum limited detectors. The latter has shown that, surprisingly, in certain parameter regimes, the inefficiency of the detection can improve with increasing its temperature, an effect exclusively due to the strong interactions in the system. The most successful achievement of the project is probably the proposed definition of heat and work for driven open quantum systems based on the identification of work- and heatlike contributions to the evolution of a density matrix along single quantum trajectories. The work, published in Phys. Rev. Lett., showed that the work statistics is affected by the presence of the heat-like contributions and that its elimination by a quantum feedback restores the correct work distribution and the proper fluctuation theorem. Though the results are first steps in the direction of analyzing heat and work along single quantum trajectories, they opened up this possibility. Our work triggered experiments in the field, further works, and an ongoing debate about possible different definitions of thermodynamic quantities, and their implications.
Publications
- Measuring cotunneling in its wake. Phys. Rev. B 90, 205413 (2014)
Oded Zilberberg, Assaf Carmi, and Alessandro Romito
(See online at https://doi.org/10.1103/PhysRevB.90.205413) - On-demand maximally entangled states with a parity meter and continuous feedback. Phys. Rev. B 90, 155438 (2014)
Clemens Meyer zu Rheda, Geraldine Haack, and Alessandro Romito
(See online at https://doi.org/10.1103/PhysRevB.90.155438) - Thermodynamics of weakly measured quantum systems. Phys. Rev. Lett. 116, 080403 (2016)
Jose Joaquin Alonso, Eric Lutz, Alessandro Romito
(See online at https://doi.org/10.1103/PhysRevLett.116.080403) - Effect of interactions on quantum-limited detectors. Phys. Rev. B 95, 205402 (2017)
Gleb Skorobagatko, Anton Bruch, Silvia Vila Kusminsky, Alessandro Romito
(See online at https://doi.org/10.1103/PhysRevB.95.205402)
