Electra Eleftheriadou, University of Strathclyde
In practical applications of communication schemes it is often necessary to amplify the transmitted signals. Because of the intrinsic noise due to Heisenberg's uncertainty principle, a quantum signal requires an amplification process which is different than the one used for classical signals.
There are many schemes that realise the amplification of quantum signals in a non-deterministic manner. Some require single photons and therefore have low success probability (~1 - 10%), whereas others are based on noise addition and as a result they cannot achieve a very high delity of the amplified state with the desired state.
In my talk I will introduce a scheme for non-deterministic amplification of coherent states, based on coherent state comparison and photon subtraction. Coherent states are much simpler to produce and handle than single photons. Moreover, their use in our scheme results in a high probability of success (~40-50%) and high fidelity (> 90%) of the output with the desired state. I will show that under certain circumstances it can even produce an amplified state with perfect fidelity (100%), in which case the device can find applications as a quantum optical repeater that increases the transmission distance of quantum states in a communications system.