Quantum metrology in the presence of dissipation with superconducting qubits.

Omar Bachain, Elhabib Jaloum, Mohamed Amazioug +4 more

Peng Xie, Xing-chen Wang, Jingwei Wang +5 more

We propose a scheme to dissipatively stabilize superpositions of squeezed coherent states for single- and two-resonator modes in superconducting circuits, where a superconducting qubit is coupled to a single or two parametrically driven transmission-line resonators with different circuit designs. A modulated magnetic flux applied to the qubit can periodically break the inversion symmetry of the qubit and induce both the parametrically enhanced transverse and longitudinal couplings to the resonators, resulting in strong nonlinear two-photon interactions between the qubit and the resonators and enabling the scheme to be implemented in a relatively weak coupling regime. With an additional microwave drive applied to the qubit, the dissipation of the qubit used as a resource can help drive the resonators into the desired superpositions of squeezed coherent states at a steady state with high speed. Numerical simulations show that the target states with high fidelity and highly nonlinear properties can be created for a long time even in the presence of photon leakage out of the resonators. The scheme can be generalized to other quantum platforms and may have potential applications in the field of quantum information processing and the improvement of estimation precision in quantum metrology.

Sahel Ashhab

Jiahao Lu, Wen Ning, Fan Wu +6 more

Critical systems near quantum phase transitions were predicted to be useful for improvement of metrological precision, thanks to their ultrasensitive response to tiny variations of the control Hamiltonian. However, realizing criticality enhanced quantum metrology is experimentally challenging, mainly owing to decoherence and critical slowing down associated with the corresponding quantum state preparation. We circumvent these problems by making use of the critical behaviors in the Jaynes-Cummings model, to which the signal field is coupled. The information is encoded in the qubit's excitation number, which displays a divergent changing rate at the critical point, and is extremely robust against decoherence and nonadiabatic effects. We demonstrate such a metrological protocol in a superconducting circuit, where an Xmon qubit, interacting with a resonator, is used as a probe for estimating the amplitude of a microwave field. The measured quantum Fisher information exhibits a critical quantum enhancement, confirming the potential for quantum metrology.

Michael Hatridge

S. Salimian, Mohammad Kazem Tavassoly