One-step implementation of a hybrid Fredkin gate with quantum memories and single superconducting qubit in circuit QED and its applications

Abstract

In a recent remarkable experiment [Sci. Adv. 2, e1501531 (2016)], a 3-qubit quantum Fredkin (i.e., controlled-SWAP) gate was demonstrated by using linear optics. Here we propose a simple experimental scheme by utilizing the dispersive interaction in superconducting quantum circuit to implement a hybrid Fredkin gate with a superconducting flux qubit as the control qubit and two separated quantum memories as the target qudits. The quantum memories considered here are prepared by the superconducting coplanar waveguide resonators or nitrogen-vacancy center ensembles. In particular, it is shown that this Fredkin gate can be realized using a single-step operation and more importantly, each target qudit can be in an arbitrary state with arbitrary degrees of freedom. Furthermore, we show that this experimental scheme has many potential applications in quantum computation and quantum information processing such as generating arbitrary entangled states (discrete-variable states or continuous-variable states) of the two memories, measuring the fidelity and the entanglement between the two memories. With state-of-the-art circuit QED technology, the numerical simulation is performed to demonstrate that two-memory NOON states, entangled coherent states, and entangled cat states can be efficiently synthesized.

Faster quantum computation with permutations and resonant couplings

“…Exchange interactions can potentially be implemented accurately even at a non-zero temperature [18] in an experimental setting. The quantum Fredkin gate is a controlled swap gate, and has been extensively studied [19][20][21] since its introduction [22]. While the quantum Fredkin gate is more challenging to implement than simple exchange, recent work suggests that it can be implemented using physically realistic resonant interactions on superconducting qubits in a single timestep [21].…”

Quantum-inspired Fredkin gate based on spatial modes of light

“…Additional theoretical work has considered a quantum version using single atoms and single photons [7,8,9,10]. Current experimental work includes nuclear magnetic resonance (NMR) [11], superconducting quantum circuits [12], DNA enzymes [13], weak coherent pulses [14,15] and linear optics with quantum-entangled photons [16]. Generally speaking the results obtained in these experiments are far from ideal.…”

Creation of superposition of arbitrary states encoded in two high-Q cavities

“…Hence, 3D cavities are good memory elements, which can have coherence time at least four orders of magnitude longer than the transmons. By encoding quantum information in microwave cavities, many schemes have been proposed for synthesizing Bell states [19], NOON states [20][21][22][23][24][25][26], and entangled coherent states [27,28] of multiple cavities, and realizing cross-Kerr nonlinearity interaction between two cavities [29,30].…”