Scientists find way to safely back up quantum data

Researchers at the University of Waterloo have demonstrated the first method for securely duplicating encrypted quantum information, allowing quantum data to be backed up without violating fundamental physical laws.

The work shows that encrypted qubits can be copied safely when protected by one-time-use encryption keys. The method preserves the limits imposed by quantum mechanics while enabling multiple redundant copies of quantum data.

The findings were published in Physical Review Letters and point toward practical quantum cloud storage and distributed quantum computing systems.

Quantum information is stored in qubits, which can be realized using particles such as electrons, photons, atoms, or ions. Qubits behave differently from classical bits and can hold information in shared states that only emerge when multiple qubits are combined.

This property allows quantum systems to store vast amounts of information through entanglement. However, it also leads to the no-cloning theorem, which states that unknown quantum information cannot be copied directly.

According to the researchers, the new approach bypasses this limitation by encrypting quantum information during the copying process. Each encrypted copy can exist simultaneously, but decryption is possible only once.

Achim Kempf, who led the research, said the technique enables secure and redundant quantum data storage across multiple servers. He said the method supports the development of large-scale quantum computing infrastructure.

The encryption relies on keys that automatically expire after a single use. Once one encrypted copy is decrypted, the key becomes invalid, preventing any further access to the remaining copies.

Koji Yamaguchi, who co-developed the method, said the approach allows many encrypted copies to be created without breaking quantum rules. He said even single-use access is sufficient for key applications such as backup and secure cloud services.

The researchers emphasized that the method does not weaken the no-cloning theorem. Instead, it works within its constraints by ensuring that usable quantum information is never duplicated.

The result supports the feasibility of future quantum cloud platforms designed for secure storage, backup, and distributed processing of quantum information.