The coherent nonlinear process where a single photon simultaneously excites two or more two-level systems (qubits) in a single-mode resonator has recently been theoretically predicted. Here we explore the case where the two qubits are placed in different resonators in an array of two or three weakly coupled resonators. Investigating different setups and excitation schemes, we show that this process can still occur with a probability approaching one under specific conditions. The obtained results provide interesting insights into subtle causality issues underlying the simultaneous excitation processes of qubits placed in different resonators.
The coherent nonlinear process where a single photon simultaneously excites two or more two-level systems (qubits) in a single-mode resonator has recently been theoretically predicted. Here we explore the case where the two qubits are placed in different resonators in an array of two or three weakly coupled resonators. Investigating different setups and excitation schemes, we show that this process can still occur with a probability approaching one under specific conditions. The obtained results provide interesting insights into subtle causality issues underlying the simultaneous excitation processes of qubits placed in different resonators.
We consider two separate atoms interacting with a single-mode optical resonator. When the frequency of the resonator field is twice the atomic transition frequency, we show that there exists a resonant coupling between one photon and two atoms, via intermediate virtual states connected by counter-rotating processes. If the resonator is prepared in its one-photon state, the photon can be jointly absorbed by the two atoms in their ground state which will both reach their excited state with probability close to one. Like ordinary quantum Rabi oscillations, this process is coherent and reversible, so that two atoms in their excited state will undergo a downward transition jointly emitting a single cavity photon. This joint absorption and emission processes can also occur with three atoms. The parameters used to investigate this process correspond to experimentally demonstrated values in circuit quantum electrodynamics systems.
We consider two separate atoms interacting with a single-mode optical or microwave resonator. When the frequency of the resonator field is twice the atomic transition frequency, we show that there exists a resonant coupling between one photon and two atoms, via intermediate virtual states connected by counterrotating processes. If the resonator is prepared in its one-photon state, the photon can be jointly absorbed by the two atoms in their ground state which will both reach their excited state with a probability close to one. Like ordinary quantum Rabi oscillations, this process is coherent and reversible, so that two atoms in their excited state will undergo a downward transition jointly emitting a single cavity photon. This joint absorption and emission process can also occur with three atoms. The parameters used to investigate this process correspond to experimentally demonstrated values in circuit quantum electrodynamics systems.
We investigate theoretically the model of two "qubits" system (one qubit having an auxiliary level) interacting with a single-mode resonator in the ultrastrong coupling regime. We show that a single photon could simultaneously excite two qubits without breaking the parity symmetry of system by properly encoding the excited states of qubits. The optimal parameter regime for achieving high probability approaching one is identified in the case of ignoring the system dissipation. Moreover, using experimentally feasible parameters, we also analyze the dissipation dynamics of the system, and present the realization of two-qubit excitation induced by single-photon. This work offers an alternative approach to realize the single-photon-induced two qubits excitation, which should advance the development of single-photon quantum technologies and have potential applications in quantum information science.
The coherent process that a single photon simultaneously excites two qubits has recently been theoretically predicted by Garziano et al. [L. Garziano, V. Macr\`{\i}, R. Stassi, O. Di Stefano, F. Nori, and S. Savasta, One Photon Can Simultaneously Excite two or More Atoms, Phys. Rev. Lett. 117, 043601 (2016)]. We propose a different approach to observe a similar dynamical process based on a superconducting quantum circuit, where two coupled flux qubits longitudinally interact with the same resonator. We show that this simultaneous excitation of two qubits (assuming that the sum of their transition frequencies is close to the cavity frequency) is related to the counter-rotating terms in the dipole-dipole coupling between two qubits, and the standard rotating-wave approximation is not valid here. By numerically simulating the adiabatic Landau-Zener transition and Rabi-oscillation effects, we clearly verify that the energy of a single photon can excite two qubits via higher-order transitions induced by the longitudinal couplings and the counter-rotating terms. Compared with previous studies, the coherent dynamics in our system only involves one intermediate state and, thus, exhibits a much faster rate. We also find transition paths which can interfere. Finally, by discussing how to control the two longitudinal-coupling strengths, we find a method to observe both constructive and destructive interference phenomena in our system.
Abstract In this paper, we present a theoretical investigation of multiphoton processes between a single atom and a multimode optical or microwave field. At first, we examine two-photon excitation, which involves the simultaneous excitation of two photons in different cavity modes by a single atom. We demonstrate that when the transition frequency of an atom is equal to the sum of the frequencies of two cavity modes, there exists a resonant coupling between the atom and the two-mode cavity field, which leads to the simultaneous excitation of the two cavity photons with the atom initially in its excited state. Moreover, we found that this coupling is coherent and reversible, allowing the atom initially in the ground state to simultaneously absorb all the photons from the cavities and transit to its excited state. Finally, we also show that this coherent interaction, in principle, can be extended to describe multiphoton processes between a single atom and a multimode cavity field, such as a three-mode cavity. The parameters used in the numerical simulation are based on the experimentally demonstrated values in circuit quantum electrodynamics systems.
The absorption of a single photon by a single two-level system (TLS) in free space is a fundamental physical process. In this contribution, we present the experimental realization of a model system to simulate the dynamics of such an absorption experiment: Comparing the absorption process of a single photon by a single TLS and the incoupling dynamics of an optical resonator, one finds an analogy between the energy stored inside the resonator and the probability of the photon to be absorbed by the TLS [1]. Both systems, resonators and TLS, respond in an equivalent way to the temporal profile of the incident light pulse. The energy storage in a resonator as well as the absorption of a single photon by a TLS can reach an unit efficiency under idealized conditions. Such an optimized process is achieved by an exponentially rising incident light field with a time constant which matches the lifetime of the system [2]. For such a perfect coupling, the end mirror of the resonator needs to have a reflectivity of unity. This corresponds to the excitation of a TLS from the complete solid angle. For a smaller reflectivity of the end mirror, the cavity simulates the absorption dynamics in the case of excitation from only a part of the solid angle. However, using real mirrors, a good analogy with excitation from a large solid angle can still be obtained by using a strongly asymmetric resonator, i.e. an incoupling mirror which has a significantly lower reflectivity than the end mirror of the cavity.