Lifting the bandwidth limit of optical homodyne measurement with broadband parametric amplification

Abstract

Homodyne measurement is a corner-stone method of quantum optics that measures the quadratures of light—the quantum optical analog of the canonical position and momentum. Standard homodyne, however, suffers from a severe bandwidth limitation: while the bandwidth of optical states can span many THz, standard homodyne is inherently limited to the electronically accessible MHz-to-GHz range, leaving a dramatic gap between relevant optical phenomena and the measurement capability. We demonstrate a fully parallel optical homodyne measurement across an arbitrary optical bandwidth, effectively lifting this bandwidth limitation completely. Using optical parametric amplification, which amplifies one quadrature while attenuating the other, we measure quadrature squeezing of 1.7 dB simultaneously across 55 THz, using the pump as the only local oscillator. As opposed to standard homodyne, our measurement is robust to detection inefficiency, and was obtained with >50% detection loss. Broadband parametric homodyne opens a wide window for parallel processing of quantum information.

Nonlinear Mach–Zehnder interferometer with ultrabroadband squeezed light

“…On the one hand, when the second crystal is calibrated, i.e. the values of r 2 ( ) and ψ 0 2 ( ) are known with high precision, observation of an interferometric picture in accordance with Equation (11) can be interpreted as 'ultrabroadband nonlinear homodyne measurement' (14) of the squeezed light produced by the first crystal. On the other hand, Equation (11) can be used for the measurement of small phase shifts introduced by a dispersive sample between the crystals.…”

“…Recently a method was proposed (14) to measure quadrature squeezing by using a Mach-Zehnder nonlinear interferometer (6,7). The mean number of photons at the output of the second amplifier scales then as the variance of a certain quadrature at the output of the first amplifier; the phase of the quadrature under test depends on the phases of the pump, signal, and idler photons inside the interferometer.…”

“…The aim of this article is to consider a nonlinear interferometer consisting of two aperiodically poled crystals placed into a common pump and generating broadband twin beams through high-gain PDC. The long-term motivation for considering this configuration is twofold: (i) measuring the broadband squeezing, produced by the first crystal (14), to determine the frequency band available for quantum operations, and (ii) measuring the phase shift introduced by a sample between the crystals in a wide band of frequencies (15,16). Our short-term objectives are building an analytic model of such an interferometer and observing the interference fringes as well as their displacement caused by the sample.…”

Persistent Coherent Beating in Coupled Parametric Oscillators

“…In modern physics, the optical parametric oscillator (OPO) is widely known due to its applications in classical and quantum optics. Below the oscillation threshold, the OPO generates squeezed vacuum [1][2][3][4], with applications in metrology [5][6][7][8], micro-and nano-electromechanical systems [9][10][11][12], quantum information [13][14][15][16] and quantum communications [17,18]. Above threshold, an OPO is the primary source of coherent light at wavelengths that are not laser accessible.…”

Pairwise mode-locking of coupled parametric oscillators

“…The parametric oscillator (PO) is a central device in modern quantum optics -a fundamental type of oscillator whose internal parameters are modulated by an external drive, leading to parametric amplification [1][2][3][4]. Below the oscillation threshold, parametric oscillators are extensively used as sources of squeezed non-classical light, where the quantum fluctuations of one quadrature of the field are reduced below the vacuum (shot-noise) level, at the expense of increased fluctuations in the orthogonal quadrature [5][6][7][8], with applications in metrology [9][10][11][12], basic quantum information [13][14][15][16] and quantum communication [17,18]. Recently, parametric oscillators have been proposed as scalable sources for continuous-variable (CV) cluster states [19] -the central resource for CV oneway quantum computation, by mixing and coupling between the modes of the frequency comb of a parametric oscillator [20].…”