Exchange unknown quantum states with almost invisible photons

Area of Science:

• Quantum Information Science
• Quantum Communication
• Quantum Computing

Background:

• Standard counterfactual quantum communication relies on measurements.
• Exchanging quantum states between different systems (e.g., photon and atom) presents unique challenges.

Purpose of the Study:

• To propose a quasi-counterfactual quantum swap gate for state exchange between a photon and an atom.
• To develop a protocol with controllable photon presence in the transmission channel.
• To achieve high fidelity and efficiency in quantum state transfer.

Main Methods:

• Utilizing multiple phase operations instead of measurements for quantum state exchange.
• Implementing a unitary time evolution operator to govern the state transfer.
• Controlling the probability of photon presence in the transmission channel.

Main Results:

• The proposed protocol achieves perfect communication fidelity and efficiency in the absence of noise and imperfections.
• The quantum state exchange is facilitated through phase operations, simplifying implementation.
• The protocol is shown to be easily convertible to a standard counterfactual protocol.

Conclusions:

• The quasi-counterfactual quantum swap gate offers a more practical approach to quantum state exchange.
• This method enhances the feasibility of counterfactual quantum communication protocols.
• The protocol's simplicity and high performance make it a valuable contribution to quantum information science.