Researchers have conducted a study to test the quantumness of IBM’s quantum computer, IBM Quantum System One. The goal of the study was to investigate the entanglement of generalized n-qubit GHZ states by measuring Bell inequalities. These Bell inequalities are derived from non-adaptive measurement-based quantum computation (NMQC), a type of quantum computing that relies on the violation of a multipartite Bell inequality to successfully compute a non-linear function.
The researchers aimed to differentiate between non-local correlations and local hidden variables (LHVs) by computing multivariate Boolean functions. LHVs can only compute linear functions, while quantum correlations can output any possible Boolean function, serving as an indicator of multipartite entanglement. They used NMQC on IBM’s quantum computer to compute various non-linear functions and demonstrate that this method can be used to characterize quantum devices.
The study found a violation of Bell inequalities for a maximum of seven qubits, showcasing the non-classical properties of IBM Quantum System One. The results were compared to a previous implementation of NMQC using photons.
Benchmarking quantum devices becomes crucial in the NISQ era, where commercially available quantum computers with 10s to 100s of noisy qubits are being used. Benchmarking protocols aim to capture the complexity and performance of quantum machines, going beyond hardware characteristics. Application benchmarks, such as the generation and verification of entanglement, provide valuable insights into the capabilities of quantum devices.
NMQC is a method used to compute multivariate functions by utilizing non-adaptive measurements on an l-qubit resource state. If the measurement statistics are described by local hidden variables, the output is restricted to linear functions. In this study, NMQC was implemented on IBM Quantum System One, demonstrating multipartite entanglement for various function sizes.
This research contributes to our understanding of quantum devices and their quantumness. It highlights the potential and limitations of IBM’s quantum computer, providing valuable insights for future quantum computing applications.
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