Quantum non-demolition measurement of photon number using weak nonlinearities

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• 作者：Christopher C. Gerry ; Trung Bui
• 刊名：Physics Letters A
• 出版年：2008
• 出版时间：8 December 2008
• 年：2008
• 卷：372
• 期：48
• 页码：7101-7104
• 全文大小：246 K

文摘

We propose an alternative method for the quantum non-demolition measurement of photon numbers wherein weak cross-Kerr nonlinearities are to be used. The usual approach to quantum non-demolition measurements of quantum number involves encoding the photon number, through a cross-Kerr interaction, into a phase shift of a probe coherent state which is then detected through balanced homodyning. Weak nonlinearities produce small phase shifts which are difficult to detect and distinguish. In the method we propose, unbalanced homodyning acts as a displacement operator on the probe beam coherent state such that the cross-Kerr interaction encodes the photon number into the amplitude of a new coherent state. The value of the photon number can be determined by inefficient photon counting on the new coherent state. Our proposed method requires fewer resources than does the usual approach.