Quantum mechanics

Detector

Quantum key distribution

Homodyne detection

Direct-conversion receiver

Photon counting

Quantum optics

Photon

Laser

Physics

Optics

Beam splitter

Coherent states

Quantum

Quantum state

Physical review. A/Physical review, A

Variable measurement operators enable the optimization of strategies for testing quantum properties and the preparation of a range of quantum states. Here, we experimentally implement a weak-field homodyne detector that can continuously tune between measuring photon numbers and field quadratures. We combine a quantum signal with a coherent state on a balanced beam splitter and detect light at both output ports using photon-number-resolving transition edge sensors. We observe that the discrete difference statistics converge to the quadrature distribution of the signal as we increase the coherent state amplitude. Moreover, in a proof-of-principle demonstration of state engineering, we show the ability to control the photon-number distribution of a state that is heralded using our weak-field homodyne detector.

Tuning between photon-number and quadrature measurements with weak-field homodyne detection