Unified generation and fast emission of arbitrary single-photon multimode $W$ states

Abstract

We propose a unified scheme to generate arbitrary single-photon multimode W states in circuit QED. A three-level system (qutrit) is driven by a pump-laser pulse and coupled to N spatially separated resonators. The coupling strength for each spatial mode gi totally decide the generated single-photon N-mode W stateso arbitrary |WN can be generated just by tuning gi. We could not only generate and store W states inside resonators but also release them into transmission lines on demand. The time and fidelity for generating (or emitting) |WN can both be the same for arbitrary N . Remarkably, |WN can be emitted with probability reaching 98.9% in 20 − 50 ns depending on parameters, comparable to the recently reported fastest two-qubit gate (30 − 45 ns). Finally, the time evolution process is convenient to control since only the pump pulse is time-dependent.

Quantum-brachistochrone approach to the conversion from $W$ to Greenberger-Horne-Zeilinger states for Rydberg-atom qubits

“…In particular, maximally-entangled multiqubit states of W - [2] and GHZ [3] type are of both conceptual and practical importance in the realm of quantum-information processing (QIP) [4]. Owing to their already proven usefulness in QIP [5,6], a large number of schemes for the preparation of W [7][8][9][10][11][12][13][14][15] and GHZ states [16][17][18][19][20][21] in various physical platforms have been proposed in recent years. Among those platforms, one of the most promising ones from the standpoint of large-scale quantum computing and analog quantum simulation, is based on ensembles of neutral atoms in Rydberg states [22][23][24][25].…”

Dynamical generation of chiral $W$ and Greenberger-Horne-Zeilinger states in laser-controlled Rydberg-atom trimers

“…Two particularly prominent classes of such states are W [2] and GHZ [3] states, for which it is known that they cannot be transformed into each other through local operations and classical communication (LOCC inequivalence [1]). Owing to their demonstrated usefulness in various QIP protocols [4,5], a multitude of different schemes for the preparation of W [6][7][8][9][10][11][12][13][14][15] and GHZ states [16][17][18][19][20] in various physical platforms have been proposed in recent years.…”