Dynamic coupling of cavities to a quantum network is of major interest to distributed quantum information processing schemes based on cavity quantum electrodynamics. This can be achieved by active tuning a mediating atom-cavity system. In particular, we consider the dynamic coupling between two coupled cavities, each interacting with a two-level atom, realized by tuning one of the atoms. One atom-field system can be controlled to become maximally and minimally coupled with its counterpart, allowing high fidelity excitation confinement, Q-switching and reversible state transport. As an application, we first show that simple tuning can lead to emission of near-Gaussian single-photon pulses that is significantly different from the usual exponential decay in a passive cavity-based system. The influences of cavity loss and atomic spontaneous emission are studied in detailed numerical simulations, showing the practicality of these schemes within the reach of current experimental technology in solid-state environment. We then show that when the technique is employed to an extended coupled-cavity scheme involving a multi-level atom, arbitrary temporal superposition of single photons can be engineered in a deterministic way.
We show that a continuous-variable (CV) qudit can be constructed using quasiorthogonal cat states of a bosonic mode, when the phase encoded in each cat state is chosen appropriately. With the constructed CV qudit and the discrete-variable (DV) qudit encoded with Fock states, we propose an approach to generate the hybrid maximally entangled state of a CV qudit and a DV qudit by using two microwave cavities coupled to a superconducting flux qutrit. This proposal relies on the initial preparation of a superposition of Fock states of one cavity and the initial preparation of a cat state of the oth…
Efficient and flexible preparation of photonic NOON states in a superconducting system
Fujian Key Laboratory of Quantum Information and Quantum Optics, Fuzhou University（福建量子信息与量子光学重点实验室，福州大学）；Department of Physics, Fuzhou University（福州大学物理系）；School of Physics, Hangzhou Normal University（杭州师范大学物理学院）；Quantum Information Physics Theory Research Team, Center for Quantum Computing, RIKEN（理研量子计算中心量子信息物理理论课题组）
Nuclear spins are candidates to encode qubits or qudits due to their isolation from magnetic noise and potentially long coherence times. However, their weak coupling to external stimuli makes them hard to integrate into circuit-QED architectures, the leading technology for solid-state quantum processors. Here, we study the coupling of $^{173}$Yb(III) nuclear spin states in an [Yb(trensal)] molecule to superconducting cavities. Experiments have been performed on magnetically diluted single crystals placed on the inductors of lumped-element $LC$ superconducting resonators with characteristic fre…
Semiconductor quantum dots embedded in optical cavities are promising on-demand sources of single photons. Here, we theoretically study single photon emission from an optically driven two-photon Raman transition between the biexciton and the ground state of a quantum dot. The advantage of this process is that it allows all-optical control of the properties of the emitted single photon with a laser pulse. However, with the presence of other decay channels and excitation-induced quantum interference, on-demand emission of the single Raman photon is generally difficult to achieve. Here we show th…
It is a long-standing goal to generate robust deterministic states of light with unique quantum properties, such as squeezing, sub-Poissonian statistics and entanglement. It is of interest to consider whether such quantum states of light could be generated by exploiting interactions with free electrons, going beyond their already ubiquitous use in generating classical light. This question is motivated by developments in electron microscopy, which present a new platform for manipulating photons through their interaction with quantum free electrons. Here, we explore the shaping of photon statist…
Ultracoherent superconducting cavity-based multiqudit platform with error-resilient control
Superconducting Quantum Materials and Systems (SQMS) Center, Fermi National Accelerator Laboratory（费米国家加速器实验室超导量子材料与系统中心）；Department of Physics and Astronomy, Northwestern University（西北大学物理与天文系）
The interaction of single quantum emitters with an optical cavity enables the realization of efficient spin-photon interfaces, an essential resource for quantum networks. The dynamical control of the spontaneous emission rate of quantum emitters in cavities has important implications in quantum technologies, e.g. for shaping the emitted photons waveform, for generating quantum entanglement, or for driving coherently the optical transition while preventing photon emission. Here we demonstrate the dynamical control of the Purcell enhanced emission of a small ensemble of erbium ions doped into na…
