The realization of an all-optical transistor, in which one "gate" photon controls a "source" light beam, is a long-standing goal in optics. By stopping a light pulse in an atomic ensemble contained inside an optical resonator, we realized a device in which one stored gate photon controls the resonator transmission of subsequently applied source photons. A weak gate pulse induces bimodal transmi...

An all-optical AND gate based on optically induced nonlinear polarization rotation of a probe light in a bulk semiconductor optical amplifier is realized at a bit rate of 2.5Gbit/s. By operating the AND gate in an up and inverted wavelength conversion scheme, the extinction ratio is improved by 8dB compared with previously published work.

We have demonstrated, the first time to our knowledge, a low-input intensity high-contrast (10:1) optical AND gate based on the differential gain (optical bistability) observed in an 850 nm GaAs vertical-cavity semiconductor optical amplifier (VCSOA). The input switching power is about 6 lW, which equals to the intensity of 16 nW=lm. It is about 2 orders of magnitude lower than in in-plane semi...

Quantum computing is a form of unconventional computation utilizing quantum effects as a fundamental part of its calculations. It has already been used in practical signal encryption in the 2010 Soccer World Cup, and there is competition amongst many governments to build more powerful and practical quantum computers. Although quantum computing is the most widespread and invested in form of unco...

We extend quantum process calculus in order to describe linear optical elements. In all previous work on quantum process calculus a qubit was considered as the information encoded within a 2 dimensional Hilbert space describing the internal states of a localised particle, most often realised as polarisation information of a single photon. We extend quantum process calculus by allowing multiple ...

We explain the use of quantum process calculus to describe and analyse linear optical quantum computing (LOQC). The main idea is to define two processes, one modelling a linear optical system and the other expressing a specification, and prove that they are behaviourally equivalent. We extend the theory of behavioural equivalence in the process calculus Communicating Quantum Processes (CQP) to ...

We have measured the temporal pulse shape of a mid-infrared free electron laser using a 60 fs Ti:sapphire pulse as an optical gate. By employing a differential technique to simultaneously measure the instantaneous infrared intensity and its time derivative, we have reconstructed the pulse shape with sub-ps resolution, despite jitter the order of 50 ps between the two lasers. The experiment has ...

High-speed reconfigurable processors have been developed in recent years: they are DAP/DNA chips and DRP chips [1][2]. These devices can be changed from one context to another context at every clock cycle in a few nanoseconds. However, their die size limits the number of reconfiguration contexts of currently available DAP/DNA and DRP chips to 4–16. In contrast, optically reconfigurable gate arr...

We design a controlled-phase gate for linear optical quantum computing by using photodetectors that cannot resolve photon number. An intrinsic error-correction circuit corrects errors introduced by the detectors. Our controlled-phase gate has a 1/4 success probability. Recent development in cluster-state quantum computing has shown that a two-qubit gate with non-zero success probability can bui...