Integrated quantum photonics
As the field has progressed new quantum algorithms have been developed which provide short and long term routes towards the demonstration of the superiority of quantum computers over their classical counterparts. Cluster state computation is now generally accepted as the approach that will be used to develop a fully fledged quantum computer. Whilst development of quantum computer will require the synthesis of many different aspects of integrated optics, boson sampling seeks to demonstrate the power of quantum computation via technologies readily available and is therefore a very promising near term algorithm to doing so. In fact shortly after its proposal there were several small scale experimental demonstrations of the boson sampling algorithm
Quantum computing
The state of a three-qubit quantum computer is similarly described by an eight-dimensional vector formula_11 (or a one dimensional vector with
each vector node holding the amplitude and the state as the bit string of qubits). Here, however, the coefficients formula_12 are complex numbers, and it is the sum of the "squares" of the coefficients' absolute values, formula_13, that must equal 1. For each formula_14, the absolute value squared formula_15 gives the probability of the system being found in the formula_14-th state after a measurement. However, because a complex number encodes not just a magnitude but also a direction in the complex plane, the phase difference between any two coefficients (states) represents a meaningful parameter. This is a fundamental difference between quantum computing and probabilistic classical computing.