Manipulating Fock states of a harmonic oscillator while preserving its linearity

Kristinn Juliusson (1) , Simon Bernon (1) , Xin Zhou (1) , Vivien Schmitt (1) , Hélène Le Sueur (2) , Patrice Bertet (1) , Denis Vion (1) , Mazyar Mirahimi (3) , Pierre Rouchon (3, 4) , Daniel Esteve (1)

1 QUANTRONICS - Quantronics Group
2 CSNSM - Centre de Sciences Nucléaires et de Sciences de la Matière
3 QUANTIC - QUANTum Information Circuits
4 CAS - Centre Automatique et Systèmes

We present a scheme for controlling the quantum state of a harmonic oscillator by coupling it to an anharmonic multilevel system (MLS) with first- to second-excited-state transition on resonance with the oscillator. In this scheme, which we call ef-resonant, the spurious oscillator Kerr nonlinearity inherited from the MLS is very small, while its Fock states can still be selectively addressed via an MLS transition at a frequency that depends on the number of photons. We implement this concept in a circuit-QED setup with a microwave three-dimensional cavity (the oscillator, with frequency 6.4 GHz and quality factor QO=2×10 6) embedding a frequency tunable transmon qubit (the MLS). We characterize the system spectroscopically and demonstrate selective addressing of Fock states and a Kerr nonlinearity below 350 Hz. At times much longer than the transmon coherence times, a nonlinear cavity response with driving power is also observed and explained.

Domaines: Sciences de l'ingénieur [physics]; Automatique / Robotique

Kristinn Juliusson, Simon Bernon, Xin Zhou, Vivien Schmitt, Hélène Le Sueur, et al.. Manipulating Fock states of a harmonic oscillator while preserving its linearity. Physical Review A : Atomic, molecular, and optical physics, 2016, 94 (6), pp.063861. ⟨10.1103/PhysRevA.94.063861⟩. ⟨cea-01346391v2⟩