Reversing the weak quantum measurement for a photonic qubit

Geoff J. Pryde, Jeremy L. O’Brien, AG White +2 more

Wenjuan Li, Zhi He, Qiong Wang

Yong‐Su Kim, Young‐Wook Cho, Young-Sik Ra +1 more

We demonstrate the conditional reversal of a weak (partial-collapse) quantum measurement on a photonic qubit. The weak quantum measurement causes a nonunitary transformation of a qubit which is subsequently reversed to the original state after a successful reversing operation. Both the weak measurement and the reversal operation are implemented linear optically. The state recovery fidelity, determined by quantum process tomography, is shown to be over 94% for partial-collapse strength up to 0.9. We also experimentally study information gain due to the weak measurement and discuss the role of the reversing operation as an information erasure.

Yong‐Su Kim, Young‐Wook Cho, Young-Sik Ra +1 more

We demonstrate the conditional reversal of a weak quantum measurement on a photonic qubit. The state recovery fidelity, determined by quantum process tomography, is shown to be over 94% for partial-collapse strength up to 0.9. We also experimentally study information gain due to the weak measurement and discuss the role of the reversing operation as an information erasure.

Jeremy L. O’Brien, Geoff J. Pryde, Andrew G. White +2 more

Xiaodong Zeng, M. Al-Amri, Shi‐Yao Zhu +1 more

We present a proposal for reversing the weak (partial-collapse) quantum measurement on a cavity field with arbitrary maximum photon number. We start by putting forth a protocol to realize quantum phase gates between the cavity field and an ancilla qubit. Afterward, adopting these phase gates and some other quantum gates, we can determine the reversal of the cavity state just by observing the ancilla qubit. Compared to previous proposals, our proposal does not need any other weak measurement and can save reversal time, which is significantly important in quantum informatics and quantum computation.