Spin-based scheme for implementing an N-qubit tunable controlled phase gate in quantum dots by interference of polarized photons

Abstract

We present a scheme for direct implementation of an N-qubit tunable controlled phase gate for spin qubits in quantum dots coupled to optical cavities, resorting to spin selective dipole coupling interaction and linear optical manipulation. In the scheme, we first design a quantum entangler device to transform the operated physical qubits, which are represented by the states of the electron spins, into non-maximal hybrid entangled states with a certain probability of success via the introduction of auxiliary circularly polarized photons. Then we show that, based on this quantum entangler operation, a spin-based N-qubit tunable controlled phase gate can be probabilistically achieved by the interference and coincidence detection of polarized photons. This might lead to a useful step toward the construction of more efficient quantum circuits and quantum algorithms in solid-state qubits.