Testing the postulates of quantum mechanics with coherent states of light and homodyne detection

Quantum mechanics has withstood every experimental test thus far. However, it relies on ad-hoc postulates which require experimental verification. Over the past decade there has been a great deal of research testing these postulates, with numerous tests of Born’s rule for determining probabilities and the complex nature of the Hilbert space being carried out. Although these tests are yet to reveal any significant deviation from textbook quantum theory, it remains important to conduct such tests in different configurations and using different quantum states. Here we perform the first such test using coherent states of light in a three-arm interferometer combined with homodyne detection. Our proposed configuration requires additional assumptions, but importantly allows us to use quantum states which exist in a larger Hilbert space compared to previous tests. For testing Born’s rule, we find that the third order interference is bounded to be κ = 0.002 ± 0.004 and for testing whether quantum mechanics is complex or not we find a Peres parameter of F = 1.0000 ± 0.0003 (F = 1 corresponds to the expected complex quantum mechanics). We also design and implement a test of Glauber’s theory of optical coherence.