Double quantum dot between two superconducting leads

D. Feinberg, Thibaut Jonckheere, Jérôme Rech +3 more

Mahn‐Soo Choi, Christoph Bruder, Daniel Loss

Mahn‐Soo Choi, Christoph Bruder, Daniel Loss

We study a double quantum dot, each dot of which is tunnel coupled to superconducting leads. In the Coulomb blockade regime, a spin-dependent Josephson coupling between two superconductors is induced, as well as an antiferromagnetic Heisenberg exchange coupling between the spins on the double dot that can be tuned by the superconducting phase difference. We show that the correlated spin states---singlet or triplets---on the double dot can be probed via the Josephson current in a dc-superconducting quantum interference device setup.

Madhu Thalakulam

The radio-frequency superconducting single electron transistor (RF-SET) is a highly sensitive and fast electrometer operating near the quantum limit. The back-action current noise of the SET induces voltage fluctuations on the system it is coupled to, dephasing its charge states. Here we propose to study the back action of the RF-SET by means of a double quantum dot (DQD) and, an RF-SET electrostatically coupled to one of the two dots. The inelastic current through the DQD is very sensitive to the spectral density of the voltage fluctuations in the nearby environment. By properly choosing the dot size and inter-dot tunnel barrier thickness, one can cause inelastic process to dominate the transport processes. A measurement of the inelastic current through the double dot system can then be used to calculate the spectral density of noise associated with the RF-SET and hence its back action. The design, fabrication and characterization of an RF-SET/DQD system is discussed in this work. Real-time studies of electron dynamics in coupled dots are also addressed.

Zhuo‐Liang Cao

Coupling and controlling between arbitrary two double quantum dot molecules can be implemented using quantum dot molecular and superconducting transmission line resonator (STLR). In the large detuning region,the interaction is insensitive to both the STLR decay and thermal field. Finally,a scheme for entanglement concentration with successfully probability 50% is proposed.