All pure multipartite entangled states of qubits can be self-tested

Area of Science:

• Quantum Information Science
• Quantum Computing
• Quantum Cryptography

Background:

• Device-independent self-testing certifies quantum states using only measurement correlations.
• Bipartite systems have universal self-testing protocols for all entangled states.
• Multipartite self-testing remains a significant challenge in quantum information.

Purpose of the Study:

• To establish a universal device-independent self-testing protocol for multipartite qubit systems.
• To demonstrate that every pure n-qubit entangled state can be self-tested.
• To provide explicit Bell-scenario correlations for multipartite self-testing.

Main Methods:

• Utilizing Bell's inequalities and the violation thereof by entangled states.
• Developing explicit Bell-scenario correlations tailored for n-qubit systems.
• Analyzing correlations for self-testing up to local isometries and complex conjugation.

Main Results:

• A universal result for device-independent self-testing of pure n-qubit entangled states is proven.
• Explicit Bell-scenario correlations are provided for the self-testing of any pure n-qubit entangled state.
• The self-testing is shown to be robust, holding up to local isometries and complex conjugation.

Conclusions:

• The work bridges a critical gap in device-independent self-testing from bipartite to multipartite systems.
• The findings pave the way for robust certification of quantum states in complex quantum networks.
• This establishes a foundational result for secure quantum communication and computation.