Preparing Greenberger–Horne–Zeilinger Entangled Photon Fock States of Three Cavities Coupled by a Superconducting Flux Qutrit

Abstract

We propose a way to prepare Greenberger-Horne-Zeilinger (GHZ) entangled photon Fock states of three cavities, by using a superconducting flux qutrit coupled to the cavities. This proposal does not require the use of classical microwave pulses and measurement during the entire operation. Thus, the operation is greatly simplified and the circuit engineering complexity and cost is much reduced. The proposal is quite general and can be applied to generate three-cavity GHZ entangled photon Fock states when the three cavities are coupled by a different three-level physical system such as a superconducting charge qutrit, a transmon qutrit, or a quantum dot. PACS numbers: 03.67.-a, 42.50.Pq, 85.25.-j I. INTRODUCTIONEntanglement is one of the important properties, through which a quantum physical system can be identified to be distinguished from a classical physical system. On the other hand, entanglement is one of the cornerstones in building up a quantum machine. It plays an important role in both quantum information processing (QIP) and quantum communication (e.g., quantum teleportation, quantum secret sharing, quantum key distribution and so on). Over the past decade, experimental preparation of entanglement has been reported with various of physical systems, such as eight photons via linear optical devices [1], fourteen trapped ions [2], three spins [3], two atoms in microwave cavity QED [4], two atoms plus one cavity mode [5], and two excitions in a single quantum dot [6]. In addition, many schemes have been proposed for generating entangled states of superconducting qubits based on cavity QED [7] or via capacitive couplings [8]. Moreover, various two-qubit or three-qubit entangled states have been experimentally demonstrated with superconducting qubits coupled to a single cavity [9][10][11][12][13].Superconducting devices [14-16] play significant roles in scalable quantum computing. The physical system composed of cavities and superconducting qubits is one of the most promising candidates for QIP [14,15]. Superconducting qubits, such as flux, charge and phase qubits, have long decoherence time [17,18] and experiments have realized quantum operations in single and multiple superconducting qubits with states read out [19][20][21][22][23]. A cavity (such as coplanar waveguide, microstrip resonator and lumped-circuit resonator and so on) can act as a quantum bus, which can mediate long-distance and fast interaction between distant superconducting qubits [24][25][26][27][28][29]. In addition, superconducting qubits and microwave resonators can be fabricated with modern technology. Furthermore, the strong coupling limit between the superconducting qubits and the cavity field was predicated earlier [29,30] and has been experimentally demonstrated [31,32].So far, many theoretical proposals have been presented for the preparation of Fock states, coherent states, squeezed states, the Schördinger Cat state, and an arbitrary superposition of Fock states of a single superconducting cavity [33][34][35][36]. Recently, there is mu...

Entanglement generation and quantum information transfer between spatially-separated qubits in different cavities

“…Merkel and Wilhelm [42] proposed a theoretical scheme for creating NOON states of two resonators, which has been implemented in experiments [43]. Moreover, schemes for preparation of entangled photon Fock states or entangled coherent states of more than two cavities have been presented recently [44][45][46].…”