Entanglement-free certification of entangling gates

M. P. Almeida*, Mile Gu, Alessandro Fedrizzi, Matthew A. Broome, Timothy C. Ralph, Andrew G. White

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)
49 Downloads (Pure)


Not all quantum protocols require entanglement to outperform their classical alternatives. The nonclassical correlations that lead to a quantum advantage are conjectured to be captured by quantum discord. Here we demonstrate that discord has an immediate practical application: it allows a client who lacks the ability to generate entanglement or conduct quantum measurements to certify whether an untrusted party has entangling gates. We implement our protocol in the discrete-variable regime with photonic qubits and show its success in the presence of high levels of noise and imperfect gate operations. Our technique offers a practical method to test claims of quantum processing and to benchmark entangling operations for physical architectures in which only highly mixed states are available.

Original languageEnglish
Article number042323
Number of pages5
JournalPhysical Review A
Issue number4
Publication statusPublished - Apr 2014




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