# Spin-based single-photon transistor, dynamic random access memory, diodes and routers in semiconductors

## TL;DR

This paper introduces a novel high-speed, high-gain single-photon transistor based on giant circular birefringence induced by a single spin in a microcavity, enabling advanced quantum and classical optical devices.

## Contribution

It presents a linear optical effect-based design for a single-photon transistor, contrasting with previous nonlinear approaches, and demonstrates its versatility as diodes, routers, and memory units.

## Key findings

- Achieves THz-speed operation.
- Utilizes a single spin in a microcavity for control.
- Enables integration into quantum and classical optical networks.

## Abstract

The realization of quantum computers and quantum Internet requires not only quantum gates and quantum memories, but also transistors at single-photon levels to control the flow of information encoded on single photons. Single-photon transistor (SPT) is an optical transistor in the quantum limit, which uses a single photon to open or block a photonic channel. In sharp contrast to all previous SPT proposals which are based on single-photon nonlinearities, here I present a novel design for a high-gain and high-speed (up to THz) SPT based on a linear optical effect - giant circular birefringence (GCB) induced by a single spin in a double-sided optical microcavity. A gate photon sets the spin state via projective measurement and controls the light propagation in the optical channel. This spin-cavity transistor can be directly configured as diodes, routers, DRAM units, switches, modulators, etc. Due to the duality as quantum gate and transistor, the spin-cavity unit provides a solid-state platform ideal for future Internet - a mixture of all-optical Internet with quantum Internet.