Flying-qubit control via a three-level atom with tunable waveguide couplings

Abstract

The control of flying qubits is at the core of quantum networks. When the flying qubits are carried by singlephoton fields, the control involves not only their logical states but also their shapes. In this paper we explore a variety of flying-qubit control problems using a three-level atom with time-varying tunable couplings to two input-output channels. It is shown that one can tune the couplings of a -type atom to distribute a single photon into the two channels with arbitrary shapes, or use a -type atom or a V -type atom to catch an arbitrary-shape distributed single photon. The -type atom can also be designed to transfer a flying qubit from one channel to the other, with both the central frequency and the photon shape being converted. With a -type atom, one can shape a pair of correlated photons via cascaded emission. In all cases, analytical formulas are derived for the coupling functions to fulfill these control tasks. Their correlation properties and physical limitations are discussed as well. These results provide useful control protocols for high-fidelity quantum information transmission over complex quantum networks.

Phase-Slip Based SQUID Used as a Photon Switch in Superconducting Quantum Computation Architectures

“…Furthermore, assuming that the stationary qubit initially stay at the excited state |e⟩ (for simplicity, treating the stationary qubit as a two-level atom), when it starts releasing |1 ξ ⟩ into the waveguide, related studies [8,12] indicate that γ changes over time and satisfies the relationship…”

“…On the contrary, assuming that the stationary qubit initially remains at the ground state |g⟩, when it starts receiving |1 ξ ⟩, γ meet the relationship [8,12]…”

“…Category 4: A stationary qubit is first converted into a flying qubit, and then converted into another stationary qubit, that is, the transmission or indirect coupling of two stationary qubits of a flying qubit. At present, relevant studies [8,12] have shown that the control process of the four types of flying qubits mentioned above requires coupling matching between stationary qubits and flying qubits. That is, for controlling flying qubits with specific time-domain shapes, such as the generation, reception, conversion, or transmission of a microwave single photon, coupling needs to be regulated.…”

Catch and release of propagating bosonic field with non-Markovian giant atom

“…In quantum networks, the control of traveling quantum fields encoded with information (flying qubit) is crucial for coherent information transfer [69,70]. The quantum information between distant nodes is physically shared by catching and releasing flying qubits.…”

“…Note that the shape of released field is different from that of incident field pulse. In our current proposal, the qubit information is encoded with the vacuum and single-excitation states as others [69,70] while the shape of the pulse is not used to encode information.…”