Broadband pulsed quadrature measurements with calorimeters

Published

December 8, 2025

Author(s)

Ezad Shojaee, James R. van Meter, Karl Mayer, Scott Glancy, Emanuel Knill

Abstract

A general one-dimensional quantum optical mode is described by a shape in the time or frequency domain. A fundamental problem is to measure a quadrature operator of such a mode. If the shape is narrow in frequency this can be done by pulsed homodyne detection, in which the mode and a matched local oscillator (LO) interfere on a beamsplitter, whose output ports are monitored by photo-detectors. The quadrature value is proportional to the difference between the photo-detectors' signals. When the shape of the mode is broad in frequency, the lack of uniform response of the detectors across the spectrum prevents direct application of this technique. We show that pulsed homodyne detection can be generalized to broadband pulsed (BBP) homodyne detection setups with detectors such as calorimeters that detect total energy instead of total number of photons. This generalization has applications in quantum measurements of femto-second pulses, and, speculatively, measurement of Rindler modes to verify the temperature of Unruh radiation. Like pulsed homodyne detection, BBP homodyne detection requires choosing the LO pulse such that the subtracted signal approaches the desired quadrature measurement for large LO amplitudes. A distinctive feature of the technique is that the LO pulse does not belong to the mode of the quadrature being measured. We analyze how the implemented measurement approaches an ideal quadrature measurement with growing LO amplitude. We prove that the moments of the measurement converge to the moments of the quadrature and that the measurement distributions converge weakly.

Citation

Physical Review A

Volume

112

Pub Type

Journals

Download Paper

https://doi.org/10.1103/wmz2-5ft7

Local Download

Keywords

quantum optics, quadrature measurement, homodyne, calorimeter

Citation

Shojaee, E. , van Meter, J. , Mayer, K. , Glancy, S. and Knill, E. (2025), Broadband pulsed quadrature measurements with calorimeters, Physical Review A, [online], https://doi.org/10.1103/wmz2-5ft7, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=959407 (Accessed December 10, 2025)