A method for identifying three entangled photons includes generating a set of first, second, and third entangled photons correlated in time and interfering the first and second entangled photons based on a difference between a first optical path from an output of an optical source that generates the first entangled photon to a first optical input to an interferometric beam splitter and a second optical path from an output of the optical source that generates the second entangled photon to a second input of the interferometric beam splitter. A first electrical signal is generated in response to detection of a first photon generated by the interfering of the first and second entangled photons. A second electrical signal is generated in response to detection of a second photon generated by the interfering of the first and second entangled photons. A third electrical signal is generated in response to detection of the third entangled photon. The first photon coincidence is determined from the first, second and their electrical signals, thereby identifying three entangled photons.

A non-contact angle measuring apparatus includes a matter-wave and energy (MWE) particle source and a detector. The MWE particle source is used for generating boson or fermion particles. The detector is used for detecting a plurality peaks or valleys of an interference pattern generated by 1) the boson or fermion particles corresponding to a slit, a bump, or a hole of a first plane and 2) matter waves' wavefront-split associated with the boson or fermion particles reflected by a second plane, wherein angular locations of the plurality peaks or valleys of the interference pattern, a first distance between a joint region of the first plane and the second plane, and a second distance between the detector and the slit are used for deciding an angle between the first plane and the second plane.

A fine atomic clock includes a particle source, an MW filter, an atomic gun, a Magneto-MW Trap (MMT) unit, an energy injection unit, and a probing unit. The particle source emits particles. The MW filter receives the particles and generates a plurality of coherent MW of particle beams. The particle beams forms a virtual space-time lattice in an enclosed space. The atomic gun emits a sample. The MMT unit utilizes a magnetic field to trap the sample in the virtual space-time lattice, and utilizes the particle beams to cool down the sample. The sample corresponds to fermions or molecules. The energy injection unit injects energy into the sample to activate the sample into an excitation state. The probing unit activates emission of the sample. An emission frequency of the sample corresponds to a characteristic emission frequency of the sample, and the emission frequency generates a standard time signal.

A high-performance single-chip, integrated-optics-based OCT system is disclosed, where the length of the reference arm is digitally variable. The reference arm includes a plurality of switch stages comprising a 22 tunable wavelength-independent waveguide switch that can direct an input light signal onto either of two different-length output waveguides. In some embodiments, the directional couplers are thermo-optic based. Some embodiments include a solid-state scanning system for scanning a sample signal along a line of object points on the sample under test.

Measurement-only topological quantum computation using both projective and interferometrical measurement of topological charge is described. Various issues that would arise when realizing it in fractional quantum Hall systems are discussed.

A method for identifying three entangled photons includes generating a set of first, second, and third entangled photons correlated in time and interfering the first and second entangled photons based on a difference between a first optical path from an output of an optical source that generates the first entangled photon to a first optical input to an interferometric beam splitter and a second optical path from an output of the optical source that generates the second entangled photon to a second input of the interferometric beam splitter. A first electrical signal is generated in response to detection of a first photon generated by the interfering of the first and second entangled photons. A second electrical signal is generated in response to detection of a second photon generated by the interfering of the first and second entangled photons. A third electrical signal is generated in response to detection of the third entangled photon. The first photon coincidence is determined from the first, second and their electrical signals, thereby identifying three entangled photons.

Coherent spectroscopic methods are described, to measure the total phase difference during an extended interrogation interval between the signal delivered by a local oscillator (10) and that given by a quantum system (QS). According to one or more embodiments, the method may comprise reading out at the end of successive interrogation sub-intervals (Ti) intermediate error signals corresponding to the approximate phase difference () between the phase of the LO signal and that of the quantum system, using coherence preserving measurements; shifting at the end of each interrogation sub-intervals (Ti) the phase of the local oscillator signal, by a known correction value (.sub.(i).sub.FB) so as to avoid that the phase difference approaches the limit of the inversion region; reading out a final phase difference (f) between the phase of the prestabilized oscillator signal and that of the quantum system using a precise measurement with no restriction on the destruction; reconstructing a total phase difference over the extended interrogation interval, as the sum of the final phase difference (f) and the opposite of all the applied phase corrections figure (I).

An atomic interferometer and methods for measuring phase shifts in interference fringes using the same. The atomic interferometer has a laser beam traversing an ensemble of atoms along a first path and an optical components train with at least one alignment-insensitive beam routing element configured to reflect the laser beam along a second path that is anti-parallel with respect to the first laser beam path. Any excursion from parallelism of the second beam path with respect to the first is rigorously independent of variation of the first laser beam path in yaw parallel to an underlying plane.

Each atom in a population of atoms can be characterized by a probability density distribution (PDD). Using a shaken-lattice technique, each PDD is split into a pair of sub-PDDs. The sub-PDDs of a pair are propagated along different paths to a common endpoint of the paths, resulting in a matter-wave interference pattern that encodes a net phase between the paths, e.g., due to differential effects associated with a gravity gradient. The matter-wave interference pattern can be measured to yield a respective measurement for each atom. The measurements can be aggregated to yield a result distribution that can serve as a classical domain estimate of the quantum-domain matter-wave interference pattern, and thus of the gravity gradient. Other embodiments can determine gradients for other types of fields.

A truncated non-linear interferometer-based sensor system includes an input port that receives an optical beam and a non-linear amplifier that amplifies the optical beam with a pump beam and renders a probe beam and a conjugate beam. The system's local oscillators have a relationship with the respective beams. The system includes a sensor that transduces an input with the probe beam and the conjugate beam or their respective local oscillators. It includes one or more phase-sensitive detectors that detect a phase modulation between the respective local oscillators and the probe beam and the conjugate beam. Output from the phase-sensitive-detectors is based on the detected phase modulation. The phase-sensor-detectors include measurement circuitry that measure the phase signals. The measurement is the sum or difference of the phase signals in which the measured combination exhibit a quantum noise reduction in an intensity difference or a phase sum or an amplitude difference quadrature.