We analyze continuous-variable ͑CV͒ quantum duality induced by entanglement between the system an... more We analyze continuous-variable ͑CV͒ quantum duality induced by entanglement between the system and the meter in two feasible CV back-action evading measurements and suggest a CV analog of the quantum erasing, previously observed in the atomic interference experiments. The suggested experiments employ only the standard quantum optical devices, such as beam splitters, parametric oscillators, and homodyne detectors.
OFC/NFOEC 2007 - 2007 Conference on Optical Fiber Communication and the National Fiber Optic Engineers Conference, 2007
ABSTRACT Power characteristics and phase functions of a NALM are investigated in simulations and ... more ABSTRACT Power characteristics and phase functions of a NALM are investigated in simulations and experimentally, showing a phase-preserving nonlinear characteristics suitable for amplitude regeneration of phase-encoded signals. A negative power penalty of -1.5 dB was obtained.
Frontiers in Optics 2004/Laser Science XXII/Diffractive Optics and Micro-Optics/Optical Fabrication and Testing, 2004
We experimentally demonstrate the influence of the vector properties of light by a comparison of ... more We experimentally demonstrate the influence of the vector properties of light by a comparison of the focal intensity distribution for radially and azimuthally polarized input fields. It is shown that a radially polarized field can be focused to a spot size significantly smaller than for linear polarization.
European Conference and Exhibition on Optical Communication, 2012
ABSTRACT A novel regenerator scheme for all-optical multilevel simultaneous amplitude and phase n... more ABSTRACT A novel regenerator scheme for all-optical multilevel simultaneous amplitude and phase noise suppression is proposed. For a star-8QAM signal, consisting of two amplitude and four phase states, EVM reduction is 4 dB and 2.5 dB for the high- and low-power states, respectively. The limiting effects of the regenerator performance have been considered.
International Conference on Quantum Information, 2008
Partial measurements play an important role in several quantum information protocols with discret... more Partial measurements play an important role in several quantum information protocols with discrete and continuous variables such as state generation and cloning. Here we report on distillation of entanglement in the presence of non-Gaussian noise.
We discuss various methods to create macroscopic (bright) entangled light beams. As an example, b... more We discuss various methods to create macroscopic (bright) entangled light beams. As an example, bright squeezed vacuum is considered in detail. This state of light, obtained via high-gain parametric downconversion, manifests entanglement in both photon numbers and polarization.
ABSTRACT We introduce and experimentally implement counter-intuitive entanglement creation by loc... more ABSTRACT We introduce and experimentally implement counter-intuitive entanglement creation by locally splitting a classical mode that is part of a larger discordant state. Possible applications are quantum advantage in information encoding and assisted dense coding.
The Doppler-free, two-photon Sd' 6s 'S~/2-Sd 6s D5~2 transition in singly ionized Hg, attractive ... more The Doppler-free, two-photon Sd' 6s 'S~/2-Sd 6s D5~2 transition in singly ionized Hg, attractive as an optical-frequency standard, has been observed for the first time on a small number of Hg+ ions confined in a radio-frequency trap. The radiative lifetime of the D5~2 state and the absolute wave number of the two-photon transition were measured to be 0.090(15) s and 17 757.152(3) cm, respectively. Optical amplitude-modulation sidebands, induced by the secular (thermal) motion of the harmonically bound ions, were observed also for the first time.
We demonstrate experimentally a nonunity gain quantum nondemolition measurement based on a simple... more We demonstrate experimentally a nonunity gain quantum nondemolition measurement based on a simple homodyne measurement and recreation strategy. Although the output state is an amplified version of the input state, the device meets standard criteria for QND measurements: the transfer coefficient was measured to 1.78, and the conditional variance was measured to 0.66.
Increasing accuracy requirements in aspheric metrology make the development of absolute testing p... more Increasing accuracy requirements in aspheric metrology make the development of absolute testing procedures for aspheric surfaces important. One strategy is transferring the standard practice three-position test for spheres to aspherics. The three-position test, however, involves a cat's eye position and therefore has certain drawbacks. We propose an absolute testing method for rotationally symmetric aspherics where the cat's eye position is replaced with a radially sheared position. Together with rotational movements of the specimen, the surface deviations can be obtained in an absolute manner. To demonstrate the validity of the procedure, we present a measurement result for a sphere and compare it with a result obtained by the standard three-position test.
Quantum beats of the hyperfine levels of the 32p3/2 state of sodium have been observed in photoio... more Quantum beats of the hyperfine levels of the 32p3/2 state of sodium have been observed in photoionization. The atoms are ionized stepwise with two pulsed lasers. The photoelectron angular distribution, measured as a function of the delay between the two laser pulses, exhibits a periodic variation due to the quantum beat effect. The hyperfine splitting of the intermediate state estimated from these measurements is in good agreement with literature values.
In the case of strong focusing the smallest possible focal spot can be reached, provided one uses... more In the case of strong focusing the smallest possible focal spot can be reached, provided one uses a specially designed polarization pattern. Other optical set-ups also employing high numerical aperture imaging are likewise expected to improve performance under polarization optimization. We propose a strategy for calculating the polarization pattern required for system optimization. A single element modulating only the polarization
In an attempt to detect gravitational waves in the frequency range around a few hundred hertz, tw... more In an attempt to detect gravitational waves in the frequency range around a few hundred hertz, two detector schemes are presently being developed worldwide, narrowband acoustic (resonant bar) and broadband laser interferometric detectors.
We present a nonlinear optical loop mirror (NOLM)based 2R-regenerator setup, which is capable of ... more We present a nonlinear optical loop mirror (NOLM)based 2R-regenerator setup, which is capable of regenerating signals modulated in phase-sensitive modulation formats. In a conventional NOLM, fluctuations of the signal amplitude are converted into phase fluctuations. Therefore, it is not suitable for regeneration of signals, modulated in formats such as differential phase-shift keying (DPSK) or duobinary. In this letter, we present a modified NOLM setup for 2R-regeneration taking return-to-zero DPSK as an example.
We report lifetime measurements of the ls23d2D, ls24d2D, and ls22pZP states of lithium. The resul... more We report lifetime measurements of the ls23d2D, ls24d2D, and ls22pZP states of lithium. The results ~=14.5+_0.7ns, v=31.0_+l.0ns, and r=27.9_+l.0ns respectively were obtained by time resolved detection of the resonance fluorescence following pulsed laser excitation.
We analyze continuous-variable ͑CV͒ quantum duality induced by entanglement between the system an... more We analyze continuous-variable ͑CV͒ quantum duality induced by entanglement between the system and the meter in two feasible CV back-action evading measurements and suggest a CV analog of the quantum erasing, previously observed in the atomic interference experiments. The suggested experiments employ only the standard quantum optical devices, such as beam splitters, parametric oscillators, and homodyne detectors.
OFC/NFOEC 2007 - 2007 Conference on Optical Fiber Communication and the National Fiber Optic Engineers Conference, 2007
ABSTRACT Power characteristics and phase functions of a NALM are investigated in simulations and ... more ABSTRACT Power characteristics and phase functions of a NALM are investigated in simulations and experimentally, showing a phase-preserving nonlinear characteristics suitable for amplitude regeneration of phase-encoded signals. A negative power penalty of -1.5 dB was obtained.
Frontiers in Optics 2004/Laser Science XXII/Diffractive Optics and Micro-Optics/Optical Fabrication and Testing, 2004
We experimentally demonstrate the influence of the vector properties of light by a comparison of ... more We experimentally demonstrate the influence of the vector properties of light by a comparison of the focal intensity distribution for radially and azimuthally polarized input fields. It is shown that a radially polarized field can be focused to a spot size significantly smaller than for linear polarization.
European Conference and Exhibition on Optical Communication, 2012
ABSTRACT A novel regenerator scheme for all-optical multilevel simultaneous amplitude and phase n... more ABSTRACT A novel regenerator scheme for all-optical multilevel simultaneous amplitude and phase noise suppression is proposed. For a star-8QAM signal, consisting of two amplitude and four phase states, EVM reduction is 4 dB and 2.5 dB for the high- and low-power states, respectively. The limiting effects of the regenerator performance have been considered.
International Conference on Quantum Information, 2008
Partial measurements play an important role in several quantum information protocols with discret... more Partial measurements play an important role in several quantum information protocols with discrete and continuous variables such as state generation and cloning. Here we report on distillation of entanglement in the presence of non-Gaussian noise.
We discuss various methods to create macroscopic (bright) entangled light beams. As an example, b... more We discuss various methods to create macroscopic (bright) entangled light beams. As an example, bright squeezed vacuum is considered in detail. This state of light, obtained via high-gain parametric downconversion, manifests entanglement in both photon numbers and polarization.
ABSTRACT We introduce and experimentally implement counter-intuitive entanglement creation by loc... more ABSTRACT We introduce and experimentally implement counter-intuitive entanglement creation by locally splitting a classical mode that is part of a larger discordant state. Possible applications are quantum advantage in information encoding and assisted dense coding.
The Doppler-free, two-photon Sd' 6s 'S~/2-Sd 6s D5~2 transition in singly ionized Hg, attractive ... more The Doppler-free, two-photon Sd' 6s 'S~/2-Sd 6s D5~2 transition in singly ionized Hg, attractive as an optical-frequency standard, has been observed for the first time on a small number of Hg+ ions confined in a radio-frequency trap. The radiative lifetime of the D5~2 state and the absolute wave number of the two-photon transition were measured to be 0.090(15) s and 17 757.152(3) cm, respectively. Optical amplitude-modulation sidebands, induced by the secular (thermal) motion of the harmonically bound ions, were observed also for the first time.
We demonstrate experimentally a nonunity gain quantum nondemolition measurement based on a simple... more We demonstrate experimentally a nonunity gain quantum nondemolition measurement based on a simple homodyne measurement and recreation strategy. Although the output state is an amplified version of the input state, the device meets standard criteria for QND measurements: the transfer coefficient was measured to 1.78, and the conditional variance was measured to 0.66.
Increasing accuracy requirements in aspheric metrology make the development of absolute testing p... more Increasing accuracy requirements in aspheric metrology make the development of absolute testing procedures for aspheric surfaces important. One strategy is transferring the standard practice three-position test for spheres to aspherics. The three-position test, however, involves a cat's eye position and therefore has certain drawbacks. We propose an absolute testing method for rotationally symmetric aspherics where the cat's eye position is replaced with a radially sheared position. Together with rotational movements of the specimen, the surface deviations can be obtained in an absolute manner. To demonstrate the validity of the procedure, we present a measurement result for a sphere and compare it with a result obtained by the standard three-position test.
Quantum beats of the hyperfine levels of the 32p3/2 state of sodium have been observed in photoio... more Quantum beats of the hyperfine levels of the 32p3/2 state of sodium have been observed in photoionization. The atoms are ionized stepwise with two pulsed lasers. The photoelectron angular distribution, measured as a function of the delay between the two laser pulses, exhibits a periodic variation due to the quantum beat effect. The hyperfine splitting of the intermediate state estimated from these measurements is in good agreement with literature values.
In the case of strong focusing the smallest possible focal spot can be reached, provided one uses... more In the case of strong focusing the smallest possible focal spot can be reached, provided one uses a specially designed polarization pattern. Other optical set-ups also employing high numerical aperture imaging are likewise expected to improve performance under polarization optimization. We propose a strategy for calculating the polarization pattern required for system optimization. A single element modulating only the polarization
In an attempt to detect gravitational waves in the frequency range around a few hundred hertz, tw... more In an attempt to detect gravitational waves in the frequency range around a few hundred hertz, two detector schemes are presently being developed worldwide, narrowband acoustic (resonant bar) and broadband laser interferometric detectors.
We present a nonlinear optical loop mirror (NOLM)based 2R-regenerator setup, which is capable of ... more We present a nonlinear optical loop mirror (NOLM)based 2R-regenerator setup, which is capable of regenerating signals modulated in phase-sensitive modulation formats. In a conventional NOLM, fluctuations of the signal amplitude are converted into phase fluctuations. Therefore, it is not suitable for regeneration of signals, modulated in formats such as differential phase-shift keying (DPSK) or duobinary. In this letter, we present a modified NOLM setup for 2R-regeneration taking return-to-zero DPSK as an example.
We report lifetime measurements of the ls23d2D, ls24d2D, and ls22pZP states of lithium. The resul... more We report lifetime measurements of the ls23d2D, ls24d2D, and ls22pZP states of lithium. The results ~=14.5+_0.7ns, v=31.0_+l.0ns, and r=27.9_+l.0ns respectively were obtained by time resolved detection of the resonance fluorescence following pulsed laser excitation.
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Papers by G. Leuchs