ED-9-4
Virtual to real photon conversion using C-shunt flux qubit
16:00-16:15 30/11/2023
*Akiyoshi Tomonaga1,2,3, Hiroto Mukai2,3, Roberto Stassi3,4, Salvatore Savasta3,4, Franco Nori3,5, Fumiki Yoshihara2, Kunihiro Inomata1, Jaw-Shen Tsai2,3
1. National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8563, Japan
2. Research Institute for Science and Technology, Tokyo University of Science, Shinjuku, Tokyo 162--0825, Japan
3. Center for Quantum Computing, RIKEN, Wakoshi, Saitama 351--0198, Japan
4. Università di Messina, I-98166 Messina, Italy
5. The University of Michigan, Ann Arbor, Michigan 48109-1040, USA.
Superconducting quantum circuits can be coupled strongly to a qubit and a resonator by taking advantage of their high degree of design freedom. The ultrastrongly coupled state is one in which the coupling energy exceeds 10 percent of the energy of a single photon in the coupled resonator, and can be used to observe various nonlinear quantum phenomena.
When the ultrastrongly coupled state is expressed in terms of the product state basis of the resonator and the qubit, it appears to contain a photon even in the ground state[1]. This is called a virtual photon, which is normally unobservable, but can be extracted as a real photon by using a C-shunt flux qubit with a three-level energy structure.
We prepare the three level atom (C-shunt flux qubit), in which the upper two levels are ultrastrongly coupled to the resonator and the ground state is weakly coupled to the resonator, it is possible to turn the ultrastrong coupling on and off. This allows virtual photons in the ultrastrongly coupled state to be emitted as soon as the coupling is truned off.
In this presentation, we report the principle and experimental results of virtual photon detection using C-shunt flux qubits.
[1] R. Stassi, et al, PRL 110, 243601 (2013)
This paper was based on results obtained from JSPS KAKENHI (Grant Number JP 22K21294, and 23K13048) and a project, JPNP16007, commissioned by the New Energy and Industrial Technology Development Organization (NEDO), Japan. Supporting from Moonshot R\&D (Grant No. JPMJMS2067) is also appreciated.
