Impossibility of deleting an unknown quantum state

Area of Science:

• Quantum Information Science
• Quantum Optics
• Quantum Computing

Background:

• Quantum states, like photon polarization, cannot be perfectly cloned.
• The ability to delete quantum information is crucial for quantum computation and information storage.

Purpose of the Study:

• To investigate if quantum information from a photon's polarization state can be deleted.
• To determine if a mechanism exists to transform two identical unknown quantum states into one preserved state and one standard state.

Main Methods:

• Theoretical analysis based on the principles of quantum mechanics.
• Examination of the linearity of quantum theory in relation to information manipulation.

Main Results:

• The linearity of quantum theory prevents the perfect deletion of an arbitrary quantum state.
• An irreversible mechanism to delete quantum information, analogous to classical information deletion, does not exist.

Conclusions:

• Perfect deletion of quantum information, even irreversibly, is not possible due to quantum theory's linearity.
• This finding has implications for quantum computation, particularly in managing and overwriting quantum information.