Challenges of realizing quantum repeater and quantum memory using photon and electron spin

Rio Fukai, Tomohiro Nakagawa, Haruki Kiyama +1 more

Abstract Quantum repeaters are required for realizing long-distance quantum communication. The quantum repeater consists of a quantum memory to store quantum information and an interface between photonic flying qubits and the memory qubits. Electron spins in gate-defined quantum dots (QDs), which have a relatively long coherence time and high electrical tunability, are promising candidates for such memory qubits because the fundamental technologies of detecting and manipulating single photoelectron spins have been established. The remaining challenge for the realization of quantum repeaters is an efficient coupling between photons and electron spins in the QDs. In this study, we discuss the enhancement of the transmission and the maintenance of the incident light polarization through bull’s eye structures on gate-defined QDs on the basis of electromagnetic field simulations.

Christoph Simon, Nicolas Sangouard, Hugues de Riedmatten +3 more

Adnan N. Kadhim, Jawad A. K. Hasan, Wijdan M. Alkhalidy

T. Takagahara, Özgür Çakır

Recently, a quantum media converter from a photon qubit to an electron spin qubit was proposed for quantum repeaters. Quantum information can take several different forms and it is preferable to be able to convert among different forms. One form is the photon polarization and another is the electron spin polarization. Photons are the most convenient medium for sharing quantum information between distant locations. However, it is necessary to realize a quantum repeater in order to send the information securely over a very long distance overcoming the photon loss. A quantum repeater requires quantum information storage and the electron spin is a promising candidate of such a quantum memory because of its long decoherence time. The most important ingredient of the quantum repeater is the entanglement swapping through the Bell (correlation) measurement. We propose an optical means to carry out the correlation measurement. The advantage of this method is the nondestructive character which keeps the quantum state unchanged.

Kenneth Sharman, Faezeh Kimiaee Asadi, Stephen C. Wein +1 more

Inspired by recent developments in the control and manipulation of quantum dot nuclear spins, which allow for the transfer of an electron spin state to the surrounding nuclear-spin ensemble for storage, we propose a quantum repeater scheme that combines individual quantum dot electron spins and nuclear-spin ensembles, which serve as spin-photon interfaces and quantum memories respectively. We consider the use of low-strain quantum dots embedded in high-cooperativity optical microcavities. Quantum dot nuclear-spin ensembles allow for the long-term storage of entangled states, and heralded entanglement swapping is performed using cavity-assisted gates. We highlight the advances in quantum dot technologies required to realize our quantum repeater scheme which promises the establishment of high-fidelity entanglement over long distances with a distribution rate exceeding that of the direct transmission of photons.

Zheng-Da Li, Rui Zhang, Xu-Fei Yin +11 more