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`I.
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`A degenerate four-wave mixing (DF WM) squeezed light apparatus comprising:
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`one or more pump beams comprising an input power of no greater than about 150 mW;
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`a probe beam configured to overlap the pump beam;
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`a vapor cell comprising an atomic vapor, a first window, and a second window, wherein the
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`atomic vapor is configured to interact with the overlapped pump and probe beams to generate an
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`amplified probe beam and a conjugate beam,
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`a repump beam configured to optically pump the atomic vapor to a groundstate and decrease
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`atomic decoherence ofthe atomic vapor, and
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`a balanceddifferential detector or joint homodyne detector configured to measure squeezing
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`due to quantum correlations between the amplified probe beam and the conjugate beam,
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`wherein the pump beam, the probe beam, and the repump beam are configured to reduce
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`spontaneous emission of the atomic vapor and generate two-mode squeezed light by DFWMinthe
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`atomic vapor with squeezing of at least 3 dB below shot noise.
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`2.
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`The DFWMsqueezed light apparatus of claim 1, wherein the input power of the one or more
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`pump beamsis no greater than about SO mW.
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`3.
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`The DFWMsqueezed light apparatus of claim 1, wherein the input power of the one or more
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`pump beams is no greater than about 20 mW.
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`4.
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`5.
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`6.
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`The DFWMsqueezed light apparatus of claim 1, wherein the repump beamis cylindrical.
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`The DFWMsqueezed light apparatus of claim 4, wherein the repump beamis an annulus.
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`The DFWMsqueezed light apparatus of claim 4, wherein the repurnp beam comprises two
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`counter-propagating annular repump beams.
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`7.
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`The DFWMsqueezed light apparatus of claim 1, wherein an input powerof the repump
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`beam is no greater than about the input power of the one or more pump beams.
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`2272.3450000/MSB-19-09P
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`8.
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`The DFWMsqueezed light apparatus of claim 1, wherein the one or more pump beams, the
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`probe beam, and the vaporcell are arranged in a forward-scattering geometry.
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`9.
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`The DFWMsqueezed light apparatus of claim 1, wherein the one or more pump beams, the
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`probe beam, and the vapor cell are arranged in a backward-scatiering geometry.
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`10.
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`The DFWMsqueezed light apparatus of claim 1, wherein the two-mode DFWMsqueezed
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`light comprises squeezing of at least 6 dB belowshot noise.
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`li.
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`The DFWMsqueezed light apparatus of claim 1, wherein the balanced differential detector
`on
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`12.
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`The DFWMsqueezedlight apparatus of claim 1, wherein the joint homodyne detector
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`comprises a pair of homodyne detectors.
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`13.
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`The DFWMsqueezed light apparatus of claim 1, wherein the first and second windows have
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`a temperature greater than an exterior surface of a cylindrical wall of the vaporcell.
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`14.
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`The DFWMsqueezed light apparatus of claim 1, wherein a temperature of the vaporcell is
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`about 30 °Cto about 100 °C.
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`15.
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`The DFWMsqueezedlight apparatus of claim 14, wherein the temperature is about 35 °C to
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`about 45 °C.
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`16.
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`The DF WMsqueezed light apparatus of claim 1, wherein a longitudinal length of the vapor
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`cell is about 0.5 cm to about 10 cm.
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`17.
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`The DFWMsqueezed light apparatus of claim 1, wherein the atomic vapor comprises a
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`rubidium vapor.
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`2272.3450000/MSB-19-09P
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`18.
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`The DFWMsqueezed light apparatus of claim 1, wherein the DFWMsqueezed light
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`apparatus comprises a portable diodelaser.
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`29.
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`19.
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`The DFWMsqueezed light apparatus of claim 18, wherein the portable diade laser cormprises
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`a volume of no greater than about 100 cm?,
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`20.
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`The DFWMsqueezed light apparatus of claim 18, wherein the portable diode laser comprises
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`an cuiput power of no greater than about 150 mW.
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`21.
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`The DFWMsqueezed light apparatus of claim 1, wherein the DFWMsqueezed light
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`apparatus comprises a portable integrated photonic chip.
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`22.
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`A method of forming a low-power squeezed light source, the method comprising:
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`overlapping one or more pump beams and a probe beam, wherein the one or more pump
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`beams comiprises an input power of no greater than about 150 mW;
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`interacting an atomic vapor with the overlapped pumpand probe beams to generate an
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`amplified probe beam and a conjugate beam;
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`optically pumping the atomic vapor with a repump beam configured to decrease atomic
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`decoherence of the atomic vapor, and
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`generating two-mode squeezed light by degenerate four-wave mixing (DFWM)in the atomic
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`vapor with squeezing ofat least 3 dB below shot noise.
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`23.
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`The method of claim 22, wherein the overlapping comprises applying an input powerof the
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`one or more pump beams no greater than about 50 mW.
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`24.
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`The method of claim 22, wherein the optical pumping comprises an annular repump beam.
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`25.
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`The method of claim 22, wherein the two-mode DF WMsqueezed light comprises squeezing
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`of at least 6 dB belowshot noise.
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`26.
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`The method of claim 22, further comprising measuring an intensity-difference squeezing due
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`to quantum correlations between the amplified probe beam and the conjugate beam with a balanced
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`differential detector.
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`27.
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`The method of claim 22, further comprising measuring quadrature squeezing due to quantum
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`correlations between the amplified probe beam and the conjugate beam with a joint homodyne
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`detector.
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`2272.3450000/MSB-19-09P
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