Browsing by Subject "Quantum optics"
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Item Advances in the Study of Two-photon Interferometry: From Turbulence-free Interferometers to X-ray Ghost Microscopes(2020-01-01) Smith, Thomas Allen; Shih, Yanhua; Physics; PhysicsTwo-photon interference present in thermal light has been applied to various interferometers and imaging techniques. Differing from more traditional optical setups that use the measurement of intensity to observe single-photon interference, two-photon interference is observed through optical correlation measurements between a pair of detectors. This dissertations presents recent work in developing two separate applications of two-photon interference: turbulence-free interferometers and X-ray ghost microscopes. Inspired by the original Hanbury Brown-Twiss interferometer, which is insensitive to optical turbulence, the turbulence-free interferometers discussed here achieve path overlap of the two-photon amplitudes, resulting in the cancellation of the contributions of turbulence, i.e. turbulence-free. This mechanism is demonstrated here in the form of the two-photon double-slit interferometer and then proposed in a new type of turbulence-free, two-photon optical beats interferometer that will likely have practical applications such as turbulence-free gravitational-wave detection. Alongside the development of two-photon interferometers, two-photon, lensless ghost imaging has been developed. The lensless nature of the technique has made X-ray ghost imaging an intriguing possibility. Due to the ineffectiveness of traditional lenses on X rays, most X-ray imaging is projection-based. Unlike true, diffraction-limited point-to-point imaging (such as imaging with a lens), projection-based imaging is more comparable to the formation of a shadow. While still extremely useful, this type of imaging lacks the full resolving power one might expect with high-energy (short-wavelength) X rays. Presented here is the theory behind potential nanometer resolution in the form of diffraction-limited point-to-point imaging achievable with X-ray ghost imaging; namely, the X-ray ghost microscope. These contributions to the field of quantum optics provide an intriguing look into the fundamental nature of light and will allow for nontraditional, practical applications.Item Bright, single-spatial-mode source of frequency non-degenerate, polarization-entangled photon pairs using periodically poled KTP(Optica, 2004-07-26) Pelton, Matthew; Marsden, Philip; Ljunggren, Daniel; Tengner, Maria; Karlsson, Anders; Fragemann, Anna; Canalias, Carlota; Laurell, FredrikWe use two perpendicular crystals of periodically-poled KTP to directly generate polarization-entangled photon pairs, the majority of which are emitted into a single Gaussian spatial mode. The signal and idler photons have wavelengths of 810 nm and 1550 nm, respectively, and the photon-pair generation rate is 1.2×10⁷ sec⁻¹ for a pump power of 62 mW. The apparatus is compact, flexible, and easily to use.Item Velocity-dependent optical forces and Maxwell’s demon(Nature, 2019-09-24) Franson, J. D.An atom placed in a focused laser beam will experience a dipole force due to the gradient in the interaction energy, which is analogous to the well-known optical tweezers effect. This force will be dependent on the velocity of the atom due to the Doppler effect, which could potentially be used to implement a Maxwell’s demon. Photon scattering and other forms of dissipation can be negligibly small, which would seem to contradict quantum information proofs that a Maxwell’s demon must dissipate a minimum amount of energy. We show that the velocity dependence of the dipole force is cancelled out by another force that is related to the gradient in the phase of the laser beam. As a result, a Maxwell’s demon cannot be implemented in this way.