Distinguishing between nonorthogonal quantum states of a single nuclear spin

Gerald Waldherr, Adetunmise C. Dada, Philipp Neumann, Fedor Jelezko, Erika Andersson, Joerg Wrachtrup

Research output: Contribution to journalArticlepeer-review

30 Citations (Scopus)
128 Downloads (Pure)


An important task for quantum-information processing is optimal discrimination between two nonorthogonal quantum states, which until now has been realized only optically. Here, we present and compare experimental realizations of optimal quantum measurements for distinguishing between two nonorthogonal quantum states encoded in a single N-14 nuclear spin at a nitrogen-vacancy defect in diamond. Implemented measurement schemes are the minimum-error measurement (known as Helstrom measurement), unambiguous state discrimination using a standard projective measurement, and optimal unambiguous state discrimination [known as Ivanovic-Dieks-Peres (IDP) measurement], which utilizes a three-dimensional Hilbert space. This allows us to benchmark the IDP measurement against the standard projective measurements. Measurement efficiencies are found to be above 80% for all schemes and reach a value of 90% for the IDP measurement.

Original languageEnglish
Article number180501
JournalPhysical Review Letters
Issue number18
Publication statusPublished - 2 Nov 2012


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