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Register a new userCreation and Measurement of Broadband Squeezed Vacuum from a Ring Optical Parametric Oscillator
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We report a 65MHz-bandwidth triangular-shaped optical parametric oscillator (OPO) for squeezed vacuum generation at 860nm. The triangle structure of our OPO enables the round-trip length to reach 45mm as a ring cavity, which provides a counter circulating optical path available for introducing a probe beam or generating another squeezed vacuum. Hence our OPO is suitable for the applications in high-speed quantum information processing where two or more squeezed vacua form a complicated interferometer, like continuous-variable quantum teleportation. With a homemade, broadband and low-loss homodyne detector, a direct measurement shows 8.4dB of squeezing at 3MHz and also 2.4dB of squeezing at 100MHz.
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We report demonstrations of both quadrature squeezed vacuum and photon number difference squeezing generated in an integrated nanophotonic device. Squeezed light is generated via strongly driven spontaneous four-wave mixing below threshold in silicon nitride microring resonators. The generated light is characterized with both homodyne detection and direct measurements of photon statistics using photon number-resolving transition edge sensors. We measure $1.0(1)$~dB of broadband quadrature squeezing (${sim}4$~dB inferred on-chip) and $1.5(3)$~dB of photon number difference squeezing (${sim}7$~dB inferred on-chip). Nearly-single temporal mode operation is achieved, with measured raw unheralded second-order correlations $g^{(2)}$ as high as $1.95(1)$. Multi-photon events of over 10 photons are directly detected with rates exceeding any previous quantum optical demonstration using integrated nanophotonics. These results will have an enabling impact on scaling continuous variable quantum technology.
Using a traveling-wave OPA with two orthogonally oriented type-I BBO crystals pumped by picosecond pulses, we generate vertically and horizontally polarized squeezed vacuum states within a broad range of wavelengths and angles. Depending on the phase between these states, fluctuations in one or another Stokes parameters are suppressed below the shot-noise limit. Due to the large number of photon pairs produced, no local oscillator is required, and 3dB squeezing is observed by means of direct detection.
The standard process for the production of strongly squeezed states of light is optical parametric amplification (OPA) below threshold in dielectric media such as LiNbO3 or periodically poled KTP. Here, we present a graphical description of squeezed light generation via OPA. It visualizes the interaction between the nonlinear dielectric polarization of the medium and the electromagnetic quantum field. We explicitly focus on the transfer from the fields ground state to a squeezed vacuum state and from a coherent state to a bright squeezed state by the mediums secondorder nonlinearity, respectively. Our pictures visualize the phase dependent amplification and deamplification of quantum uncertainties and give the phase relations between all propagating electro-magnetic fields as well as the internally induced dielectric polarizations. The graphical description can also be used to describe the generation of nonclassical states of light via higherorder effects of the non-linear dielectric polarization such as four-wave mixing and the optical Kerr effect.
Laguerre-Gaussian (LG) modes, carrying orbital angular momentum of light, are critical for important applications such as high-capacity optical communications, super-resolution imaging, and multi-dimensional quantum entanglement. Advanced developments in these applications strongly demand reliable and tunable LG mode laser sources, which, however, do not yet exist. Here, we experimentally demonstrate highly-efficient, highly-pure, broadly-tunable, and topological-charge-controllable LG modes from a Janus optical parametric oscillator (OPO). Janus OPO featuring two-face cavity mode is designed to guarantee an efficient evolution from a Gaussian-shaped fundamental pumping mode to a desired LG parametric mode. The output LG mode has a tunable wavelength between 1.5 um and 1.6 um with a conversion efficiency above 15%, a topological charge switchable from -4 to 4, and a mode purity as high as 97%, which provides a high-performance solid-state light source for high-end demands in multi-dimensional multiplexing/demultiplexing, control of spin-orbital coupling between light and atoms, and so on.
In this paper we examine some foundational issues of a class of quantum engines where the system consists of a single quantum parametric oscillator, operating in an Otto cycle consisting of 4 stages of two alternating phases: the isentropic phase is detached from any bath (thus a closed system) where the natural frequency of the oscillator is changed from one value to another, and the isothermal phase where the system (now rendered open) is put in contact with one or two squeezed baths of different temperatures, whose nonequilibrium dynamics follows the Hu-Paz-Zhang (HPZ) master equation for quantum Brownian motion. The HPZ equation is an exact nonMarkovian equation which preserves the positivity of the density operator and is valid for a) all temperatures, b) arbitrary spectral density of the bath, and c) arbitrary coupling strength between the system and the bath. Taking advantage of these properties we examine some key foundational issues of theories of quantum open and squeezed systems for these two phases of the quantum Otto engines. This include, i) the nonMarkovian regimes for non-Ohmic, low temperature baths, ii) what to expect in nonadiabatic frequency modulations, iii) strong system-bath coupling, as well as iv) the proper junction conditions between these two phases. Our aim here is not to present ways for attaining higher efficiency but to build a more solid theoretical foundation for quantum engines of continuous variables covering a broader range of parameter spaces hopefully of use for exploring such possibilities.
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