[Seminar] "Quantum microwaves with a DC-biased Josephson junction" by Dr. Iouri Moukharski

Dr. Iouri Moukharski, CNRS/CEA Saclay

Title: "Quantum microwaves with a DC-biased Josephson junction"

Abstract:   Tunneling of a Cooper pair through a dc-biased Josephson junction is possible only if collective excitations (photons) are produced in the rest of the circuit to conserve the energy. The probability of tunneling and photon creation, well described by the theory of dynamical Coulomb blockade, increases with the coupling strength between the tunneling charge and the circuit mode, which scales as the mode impedance. Using very simple circuits with only one or two low impedance series resonators, we first show the equality between Cooper pair tunneling rate and photon production rate [1]. Then we demonstrate a blockade regime for which the presence of a single photon blocks the next tunneling event and the creation of a second photon [2]. Finally, using two resonators with different frequencies, we demonstrate photon pair production [3], two-mode squeezing, and entanglement between the two modes leaking out of the resonators.

[1] M. Hofheinz et al., Phys. Rev. Lett. 106, 217005 (2011)

[2] Rolland, C., et al., Phys. Rev. Lett. 122(18), 186804 (2019).

[3] M. Westig et al., Phys. Rev. Lett. 119 (13), 137001 (2017)