A scheme for efficient quantum computation with linear optics

Abstract

Quantum computers promise to increase greatly the efficiency of solving problems such as factoring large integers, combinatorial optimization and quantum physics simulation. One of the greatest challenges now is to implement the basic quantum-computational elements in a physical system and to demonstrate that they can be reliably and scalably controlled. One of the earliest proposals for quantum computation is based on implementing a quantum bit with two optical modes containing one photon. The proposal is appealing because of the ease with which photon interference can be observed. Until now, it suffered from the requirement for non-linear couplings between optical modes containing few photons. Here we show that efficient quantum computation is possible using only beam splitters, phase shifters, single photon sources and photo-detectors. Our methods exploit feedback from photo-detectors and are robust against errors from photon loss and detector inefficiency. The basic elements are accessible to experimental investigation with current technology.

Bright solid-state sources of indistinguishable single photons

“…T he quantum interference 1 of two indistinguishable single photons is an important resource for long distance quantum communication and linear quantum computing [2][3][4][5] . Recent years have seen important progress in the development of bright single-photon sources in solid-state systems using semiconductor self-assembled quantum dots (QDs) 6 inserted in photonic structures [7][8][9][10] .…”

Practical photon number detection with electric field-modulated silicon avalanche photodiodes

“…To further investigate the photon number dependence of the electric field-modulated Si-APD, we used an oscilloscope to record the distribution of output voltage pulses obtained from around 5×10 6 samples. Figure 3a,b shows the measured probability distribution for detected photon fluxes of µ′ = 4.8 and 0.9, respectively (detected per pulse).…”

“…For example, in quantum teleportation 4 and entanglement swapping 5 schemes used in quantum repeaters, a Bell state measurement applied upon two single photons arriving concurrently at a beam splitter requires number states N = 0, 1 or 2 to be distinguished in each detector. Similarly, in linear optics quantum computing, the successful operation of a quantum logic gate is often heralded by the detection of a photon number state 6 . Low-noise photon number detection would also be useful for characterizing non-classical light sources 7,8 and security analysis in quantum cryptography 9 .…”

Physics: Unite to build a quantum Internet

“…Simple optics and photodetectors can distinguish two, at most. Extra qubits add technical complications 5 .…”