Quantum Computing: Linear Optics Implementations

TL;DR

This paper reviews and advances linear optics methods for implementing two-photon quantum gates, focusing on increasing success probabilities through postcorrection techniques and complex setups.

Contribution

It introduces new postcorrection strategies and analyzes multiport physics to enhance two-photon gate success rates in linear optical quantum computing.

Findings

Postcorrection techniques can improve gate success probability.

Single beam splitter correction is insufficient for state correction.

Complex setups with multiple beam splitters may increase success rates.

Abstract

One of the main problems that optical quantum computing has to overcome is the efficient construction of two-photon gates. Theoretically these gates can be realized using Kerr-nonlinearities, but the techniques involved are experimentally very difficult. We therefore employ linear optics with projective measurements to generate these non-linearities. The downside is that the measurement-induced nonlinearities achieved with linear optics are less versatile and the success rate can be quite low. This project is mainly the result of a literature study but also a theoretical work on the physics behind quantum optical multiports which is essential for realizing two-photon gates. By applying different postcorrection techniques we increase the probability of success in a modifed non-linear sign shift gate which is foundational for the two photon controlled-NOT gate. We prove that it's not possible to correct the states by only using a single beam splitter. We show that it might be possible to increase the probability of success using a more complex setup with at least two error-correcting beam splitters.