| dc.description.abstract | Quantum measurement is the cornerstone of quantum computing and quantum information. It
has many exciting applications. Various quantum optical systems are key to experimental physics
because of their high precision and well controllability. In this dissertation, we focus on study of
quantum measurement and its applications in quantum optical systems. We first study the fundamental
trade-off relation between information gain and fidelity during successive weak QND
measurement. Then we evaluate the effectiveness of quantum measurement reversal on quantum
state protection under non-ideal detection efficiency. A linear optical setup is proposed for experimental
verification of our result. Finally, we explore the performance of non-Gaussian two-mode
entangled states for quantum illumination, which is an application of quantum state discrimination.
For successive weak QND measurements, we show that the information gain increases monotonically
with respect to the number of measurements. Meanwhile the fidelity shows oscillatory
decreasing behavior, which results from interference terms between photon numbers. We conclude
that a greater information gain does not always imply a worse fidelity. For non-ideal quantum measurement
reversal, we derive how quantum states evolve in quantum reversal under finite effective
monitoring efficiency. Fidelity and concurrence are then calculated to evaluate the effectiveness
of state protection using reversal. Generally the performance is weakened by finite monitoring
efficiency. The negative effect of measurement reversal can dominate under certain conditions. A
criterion that decides whether to apply state protection using measurement reversal is given. As
for quantum illumination, we conclude that non-Gaussian operations can enhance the performance,
i.e., achieve lower error probability by introducing both stronger entanglement and larger average
photon numbers. However, if the signal strength is a concern, two-mode squeezed states (TMSS)
performs better than other non-Gaussian states under the same output signal strength. When applying
a coherent superposition of photon subtraction and photon addition to enhance quantum
illumination, we show that optimal error probability is achieved by an asymmetrical operation. | en |
