Optical Signal Regeneration

Abstract

In this chapter the different means for all‐optical signal regeneration are outlined. 3R regeneration implies signal reshaping and retiming and is based on optical decision circuits and devices for optical clock extraction respectively. In what follows, it will become clear that most of the optical decision circuits are based on active interferometers while devices for clock recovery are generally self‐pulsating laser diodes.

Towards Quantum Repeaters with Solid-State Qubits: Spin-Photon Entanglement Generation Using Self-assembled Quantum Dots

“…With this resource in place, teleportation [28] can be used to transmit an arbitrary qubit from one end of the network to the other. 8 Repeaters in classical communication serve another important purpose besides just amplifying the transmitted signal: they perform error correction by recreating high-quality representations of bits from low-quality representations, since distortions caused by transmission through the optical fibre ultimately lead to bit-discrimination errors if left unchecked [29]. This purpose of classical repeaters suggests an equivalent function for quantum repeaters in quantum networks: quantum repeaters should correct decoherence in the entangled qubits before the decoherence becomes so severe that it is uncorrectable.…”

“…If all the other states φ i are not very "different" from the target state |Ψ , i.e., Ψ|φ i ∼ 1, then the reduction in fidelity from measuring the mixed state ρ, as opposed to the heralded ensemble of target states, will not be severe. However, in many situations, there will be some states φ i that are nearly orthogonal to |Ψ , and have high probabilities r i of being generated, and this will dramatically decrease the measured fidelity 29. To illustrate our point, we assume here a simple entanglement-swapping-based approach to distributing entanglement, in which the adjacent nodes each attempt to become entangled with their immediate neighbours (stopping once they have succeeded), and where the protocol is reset once every pair of adjacent nodes shares an entangled qubit pair.…”