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Showing papers on "Beam splitter published in 2006"


Journal ArticleDOI
06 Apr 2006-Nature
TL;DR: The quantum interference of two single photons emitted by two independently trapped single atoms is demonstrated, bridging the gap towards the simultaneous emission of many indistinguishable single photons by different emitters.
Abstract: When two indistinguishable single photons are fed into the two input ports of a beam splitter, the photons will coalesce and leave together from the same output port. This is a quantum interference effect, which occurs because two possible paths-in which the photons leave by different output ports-interfere destructively. This effect was first observed in parametric downconversion (in which a nonlinear crystal splits a single photon into two photons of lower energy), then from two separate downconversion crystals, as well as with single photons produced one after the other by the same quantum emitter. With the recent developments in quantum information research, much attention has been devoted to this interference effect as a resource for quantum data processing using linear optics techniques. To ensure the scalability of schemes based on these ideas, it is crucial that indistinguishable photons are emitted by a collection of synchronized, but otherwise independent sources. Here we demonstrate the quantum interference of two single photons emitted by two independently trapped single atoms, bridging the gap towards the simultaneous emission of many indistinguishable single photons by different emitters. Our data analysis shows that the observed coalescence is mainly limited by wavefront matching of the light emitted by the two atoms, and to a lesser extent by the motion of each atom in its own trap.

306 citations


Patent
28 Jun 2006
TL;DR: The polarizing beam splitter (PBS) as discussed by the authors is a beamforming beamforming system that is suitable for use in projection systems and displays and has a refractive index difference of less than about 0.15 units.
Abstract: The present invention provides a unique polarizing beam splitter (PBS) that is suitable for use in projection systems and displays. The PBS contains at least one prism having at least one major surface and having a refractive index of at least about 1.6 and a birefringent film disposed on the major surface of the prism. The birefringent film is a multi-layer film having at layers of at least a first material and a second material. After uniaxial stretching, the film exhibits a refractive index difference of less than about 0.15 units in the stretched direction.

290 citations


Patent
27 Jan 2006
TL;DR: In this article, an optical system and method for data reading is presented, where the preferred system is directed to a scanner which includes a laser diode and a beam splitter for generating first optical beam and a second optical beam, the first beam being directed toward one side of a scanning optical element such as a rotating polygon mirror and to a first mirror array, the second beam being simultaneously directed toward another side of the rotating polygons mirror and then to a second and a third mirror array.
Abstract: An optical system and method for data reading. The preferred system is directed to a scanner which includes a laser diode and a beam splitter for generating first optical beam and a second optical beam, the first optical beam being directed toward one side of a scanning optical element such as a rotating polygon mirror and to a first mirror array, the second optical beam is being simultaneously directed toward a second optical element such as another side of the rotating polygon mirror and then to a second and a third mirror array. The first mirror array is configured to generate a scan pattern through a vertical window and the second and third mirror arrays are configured to generate scan patterns passing through a horizontal window. In combination, the three mirror arrays generate three sets of scan lines so as to scan the bottom and all lateral sides of an object being passed through the scan volume.

283 citations


Journal ArticleDOI
TL;DR: Bomzon et al. as discussed by the authors presented a Pancharatnam-Berry phase optical element for wave front shaping in the visible spectral domain, based on patterned liquid crystal technology, with the possibility of electro-optically switching between opposite helicities by controlling the handedness of the input circular polarization.
Abstract: We report the realization of a Pancharatnam-Berry phase optical element [Z. Bomzon, G. Biener, V. Kleiner, and E. Hasman, Opt. Lett. 27, 1141 (2002)], for wave front shaping working in the visible spectral domain, based on patterned liquid crystal technology. This device generates helical modes of visible light with the possibility of electro-optically switching between opposite helicities by controlling the handedness of the input circular polarization. By cascading this approach, fast switching among multiple wave front helicities can be achieved, with potential applications to multistate optical information encoding. The approach demonstrated here can be generalized to other polarization-controlled devices for wave front shaping, such as switchable lenses, beam splitters, and holographic elements.

274 citations


Journal ArticleDOI
TL;DR: This work describes an ultrasmall polarization splitter based on a simple directional coupler consisting of silicon wire waveguides that represents a first step towards accomplishing an Ultrasmall optical circuit with polarization diversity based on silicon wireWaveguides.
Abstract: We describe an ultrasmall polarization splitter based on a simple directional coupler consisting of silicon wire waveguides. The size is only 7 x 16 microm(2), and the polarization extinction ratio is about 15 dB for a single coupler. A double-coupler structure improves the extinction ratio to over 20 dB. The excess loss is smaller than 0.5 dB for both types of device. In the device, the shape of the high-speed waveform is retained at any angle of polarization. Our polarization splitter represents a first step towards accomplishing an ultrasmall optical circuit with polarization diversity based on silicon wire waveguides.

268 citations


Patent
15 May 2006
TL;DR: In this paper, a tissue imaging system consisting of a light source, beam shaping optics, and polarizing optics is described, where the modulator pixels optically function like pinholes relative to the illumination light and the image light.
Abstract: A tissue imaging system (200) for examining the medical condition of tissue (290) has an illumination optical system (205), which comprises a light source (220), having one or more light emitters, beam shaping optics, and polarizing optics. An optical beamsplitter (260) directs illumination light to an imaging sub-system, containing a spatial light modulator array (300). An objective lens (325) images illumination light from the spatial light modulator array to the tissue. An optical detection system (210) images the spatial light modulator to an optical detector array. A controller (360) drives the spatial light modulator to provide time variable arrangements of on-state pixels. The objective lens operates in a nominally telecentric manner relative to both the spatial light modulator and the tissue. The polarizing optics are independently and iteratively rotated to define variable polarization states relative to the tissue. The modulator pixels optically function like pinholes relative to the illumination light and the image light.

220 citations


Journal ArticleDOI
TL;DR: In this paper, the spin beam splitter in a one-dimensional mesoscopic ring with one input and two output leads was investigated, and the relevant parameters such that the device has unit efficiency.
Abstract: Quantum interference and spin-orbit interaction in a one-dimensional mesoscopic semiconductor ring with one input and two output leads can act as a spin beam splitter. Different polarization can be achieved in the two output channels from an originally totally unpolarized incoming spin state, very much like in a Stern-Gerlach apparatus. We determine the relevant parameters such that the device has unit efficiency.

149 citations


Journal ArticleDOI
TL;DR: In this article, the authors analyse the off-resonant Raman interaction of a single broadband photon, copropagating with a classical ''control'' pulse, with an atomic ensemble, showing that the classical electrodynamical structure of the interaction guarantees canonical evolution of the quantum mechanical field operators.
Abstract: We analyse the off-resonant Raman interaction of a single broadband photon, copropagating with a classical `control' pulse, with an atomic ensemble. It is shown that the classical electrodynamical structure of the interaction guarantees canonical evolution of the quantum mechanical field operators. This allows the interaction to be decomposed as a beamsplitter transformation between optical and material excitations on a mode-by-mode basis. A single, dominant modefunction describes the dynamics for arbitrary control pulse shapes. Complete transfer of the quantum state of the incident photon to a collective dark state within the ensemble can be achieved by shaping the control pulse so as to match the dominant mode to the temporal mode of the photon. Readout of the material excitation, back to the optical field, is considered in the context of the symmetry connecting the input and output modes. Finally, we show that the transverse spatial structure of the interaction is characterised by the same mode decomposition.

127 citations


Journal ArticleDOI
TL;DR: Fiber-based high-speed polarization-sensitive Fourier domain optical coherence tomography (PS-FD-OCT) is developed at 840 nm wavelength using polarization modulation method and three dimensional phase retardation images show the potentials for applying the system to biological and medical studies.
Abstract: Fiber-based high-speed polarization-sensitive Fourier domain optical coherence tomography (PS-FD-OCT) is developed at 840 nm wavelength using polarization modulation method. The incident state of polarization is modulated along B-scan. The spectrometer has a polarizing beamsplitter and two line-CCD cameras operated at a line rate of 27.7 kHz. From the 0th and 1st orders of the spatial frequencies along the B-scanning, a depth-resolved Jones matrix can be derived. Since continuous polarization modulation along B-scan causes fringe washout, equivalent discrete polarization modulation is applied to biological measurements. For the demonstration, an in vitro chicken breast muscle, an in vivo finger pad, and an in vivo caries lesion of a human tooth are measured. Three dimensional phase retardation images show the potentials for applying the system to biological and medical studies.

118 citations


Patent
08 Feb 2006
TL;DR: In this article, the authors provided an optical device, including a light wave- transmitting substrate having two major surfaces and edges, optical means for coupling light into the substrate by total internal reflection, and a plurality of partially reflecting surfaces (22a, 22b) carried by the substrate wherein the reflecting surfaces are parallel to each other and are not parallel to any of the edges of the substrate.
Abstract: There is provided an optical device, including a light waves- transmitting substrate having two major surfaces and edges, optical means for coupling light into the substrate by total internal reflection, and a plurality of partially reflecting surfaces (22a, 22b) carried by the substrate wherein the partially reflecting surfaces (22a, 22b) are parallel to each other and are not parallel to any of the edges of the substrate, and wherein one or more of the partially reflecting surfaces (22a, 22b) is an anisotropic surface.

117 citations


Patent
19 Apr 2006
TL;DR: In this paper, the authors describe a beam splitter that divides a signal from the master oscillator into two or more sub-signals, and each output head receives one of the two sub signals.
Abstract: Laser apparatus and methods involving multiple amplified outputs are disclosed. A laser apparatus may include a master oscillator, a beam splitter coupled to the master oscillator, and two or more output heads optically coupled to the beam splitter. The beam splitter divides a signal from the master oscillator into two or more sub-signals. Each output head receives one of the two or more sub-signals. Each output head includes coupling optics optically coupled to the beam splitter. An optical power amplifier is optically coupled between the beam splitter and the coupling optics. Optical outputs from the two or more output heads do not spatially overlap at a target. The master oscillator signal may be pulsed so that optical outputs of the output heads are pulsed and substantially synchronous with each other.

Journal ArticleDOI
TL;DR: The problem of optical-field measurement is transformed from one involving the choice and placement of lenses and detector arrays to that of designing geometrical constructions of polymeric, light-sensitive fibres that enables access to optical information on unprecedented length and volume scales.
Abstract: Optical fields are measured using sequential arrangements of optical components such as lenses, filters, and beam splitters in conjunction with planar arrays of point detectors placed on a common axis1. All such systems are constrained in terms of size, weight, durability and field of view. Here a new, geometric approach to optical-field measurements is presented that lifts some of the aforementioned limitations and, moreover, enables access to optical information on unprecedented length and volume scales. Tough polymeric photodetecting fibres drawn from a preform2 are woven into light-weight, low-optical-density, two- and three-dimensional constructs that measure the amplitude and phase of an electromagnetic field on very large areas. First, a three-dimensional spherical construct is used to measure the direction of illumination over 4π steradians. Second, an intensity distribution is measured by a planar array using a tomographic algorithm. Finally, both the amplitude and phase of an optical wave front are acquired with a dual-plane construct. Hence, the problem of optical-field measurement is transformed from one involving the choice and placement of lenses and detector arrays to that of designing geometrical constructions of polymeric, light-sensitive fibres.

Patent
27 Feb 2006
TL;DR: In this paper, a method for producing a solid optical system with embedded elements is presented, which may include inorganic, polymer, or hybrid lenses, mirrors, beam splitters and polarizers.
Abstract: A method for producing a solid optical system with embedded elements is provided. The embedded elements may include inorganic, polymer, or hybrid lenses, mirrors, beam splitters and polarizers, or other elements . The embedding material is a transparent high quality optical polymer.

Journal ArticleDOI
TL;DR: A principal scheme for an external cavity technique for changing the polarization of a laser beam based on a modified Sagnac interferometer is proposed and allows the generation of a longitudinally polarized electric field by sharp focusing.
Abstract: A principal scheme for an external cavity technique for changing the polarization of a laser beam based on a modified Sagnac interferometer is proposed. The modified Sagnac interferometer includes standard optical components: a displacement polarizing beam splitter, an angle reflector, and a Dove prism. The radially polarized beams, obtained with the help of the developed scheme, allow the generation of a longitudinally polarized electric field by sharp focusing. The phase correction of radially polarized modes of higher orders leads to increasing the longitudinal field in the focus of the beam.

Journal ArticleDOI
TL;DR: The design and characterization of a photonic crystal (PC) polarization beam splitter (PBS) that operates with an extinction ratio of greater than 15 dB for both polarizations are presented and it is shown that the TE- like mode has very high reflection at the interface between the two PCs, whereas the TM-like mode exhibits a very high transmission.
Abstract: The design and characterization of a photonic crystal (PC) polarization beam splitter (PBS) that operates with an extinction ratio of greater than 15 dB for both polarizations are presented. The PBS is fabricated on a silicon-on-insulator (SOI) wafer where the input and output ports consist of 5 μm wide ridge waveguides. A large spectral shift is observed in the dispersion plots of the lowest-order even (TE-like) and odd (TM-like) modes due to the SOI confinement. Because of this shift, the TE-like mode is close to a directional gap at the top of the band, and the TM-like mode is in a low-frequency regime where the dispersion surface is almost isotropic. We show that the TE-like mode has very high reflection at the interface between the two PCs, whereas the TM-like mode exhibits a very high transmission.

Journal ArticleDOI
TL;DR: A highly controllable quantum filter for photon number states, which takes advantage of a measurement-induced amplitude nonlinearity, which is demonstrated for one- and two-photon states over a wide range of beam splitter reflectivities.
Abstract: Unprecedented optical nonlinearities can be generated probabilistically in simple linear-optical networks conditioned on specific measurement outcomes. We describe a highly controllable quantum filter for photon number states, which takes advantage of such a measurement-induced amplitude nonlinearity. The basis for this filter is multiphoton nonclassical interference which we demonstrate for one- and two-photon states over a wide range of beam splitter reflectivities. Specifically, we show that the transmission probability, conditional on a specific measurement outcome, can be larger for a two-photon state than a one-photon state; this is not possible with linear optics alone.

Patent
27 Nov 2006
TL;DR: In this paper, a multivariate optical computing and analysis system is presented, which includes a light source configured to radiate a first light along a first ray path, a modulator disposed in the first-ray path, the modulator configured to modulate the first light to a desired frequency, a spectral element disposed proximate the modulators, the spectral element configured to filter the firstlight for a spectral range of interest of a sample; a cavity disposed in communication with the cavity, the cavity configured to direct the first beacon in a direction of the sample, a tube disposed
Abstract: A multivariate optical computing and analysis system includes a light source configured to radiate a first light along a first ray path; a modulator disposed in the first ray path, the modulator configured to modulate the first light to a desired frequency; a spectral element disposed proximate the modulator, the spectral element configured to filter the first light for a spectral range of interest of a sample; a cavity disposed in communication with the spectral element, the cavity configured to direct the first light in a direction of the sample; a tube disposed proximate the cavity, the tube configured to receive and direct a second light generated by a reflection of the first light from the sample, the tube being further configured to separate the first and second lights; a beamsplitter configured to split the second light into a first beam and a second beam; an optical filter mechanism disposed to receive the first beam, the optical filter mechanism configured to optically filter data carried by the first beam into at least one orthogonal component of the first beam; and a detector mechanism in communication with the optical filter mechanism to measure a property of the orthogonal component to measure the data.

Journal ArticleDOI
TL;DR: In this paper, the top silver layer was etched by a focused ion beam to mill an array of identical slits covering an area of 0.75 mm 2. This was undertaken in a manner that gave well-formed slits with minimal bridging, while at the same time minimizing the damage to the dielectric core.
Abstract: Next the top silver layer was etched by a focused ion beam to mill an array of identical slits covering an area of 0.75 mm 2 . This was undertaken in a manner that gave well-formed slits with minimal bridging, while at the same time minimizing the damage to the dielectric core. The width of each slit w50 nm is significantly less than the visible radiation wavelength, and the periodicity of the array is g =340 nm. The choice of these parameters was based upon initial modeling studies that took into account the resolution limitations of the fabrication process together with the requirement to observe well-defined resonances in the visible regime. The geometrical parameters of the structure are determined from scanning electron microscope SEM imaging Table I; an image of a typical region of the sample surface is presented in Fig. 1b. The dispersion of the modes is determined by recording the spectra of the specularly reflected beam as a function of the angle of incidence . A collimated beam from a tungsten halogen lamp was spectrally filtered by a monochromator. The intensity of the incident light was modulated using a mechanical chopper to allow lock-in detection, and a beam splitter redirected a small fraction of the incident light onto a second detector, allowing for source intensity fluctua

Patent
01 Aug 2006
TL;DR: In this paper, a free-space communication transceiver includes a telescope for transmitting and receiving laser beams, a tunable laser transmitter for generating a transmit laser beam modulated with data, and an optical receiver for processing a receive laser beam received from the telescope to recover data.
Abstract: A free-space communication transceiver includes a telescope for transmitting and receiving laser beams, a tunable laser transmitter for generating a transmit laser beam modulated with data, a tunable optical receiver for processing a receive laser beam received from the telescope to recover data, and a tunable beamsplitter that directs the transmit laser beam to the telescope and directs the receive laser beam from the telescope to the optical receiver. Between the telescope and beamsplitter, the transmit and receive laser beams travel along a common optical axis as collinear collimated free-space beams. The transmit and receive laser beams operate at different wavelengths that can be interchanged, thereby support full-duplex operation. The beamsplitter employs a tunable etalon filter whose wavelength-dependent transmission characteristics are adjusted according to the transmit and receive wavelengths. Optionally, RF signals can additionally be couple to the common optical axis and transmitted and received by the telescope.

Journal ArticleDOI
Xiaolong Su1, Aihong Tan1, Xiaojun Jia1, Qing Pan1, Changde Xie1, Kunchi Peng1 
TL;DR: In this paper, the quantum entanglement of amplitude and phase quadratures between two intense optical beams with a total intensity of 22mW and a frequency difference of 1nm, which are produced from an optical parametric oscillator operating above threshold, is experimentally demonstrated with two sets of unbalanced Mach-Zehnder interferometers.
Abstract: The quantum entanglement of amplitude and phase quadratures between two intense optical beams with a total intensity of 22mW and a frequency difference of 1nm, which are produced from an optical parametric oscillator operating above threshold, is experimentally demonstrated with two sets of unbalanced Mach-Zehnder interferometers. The measured quantum correlations of intensity and phase are in reasonable agreement with the results calculated based on a semiclassical analysis of the noise characteristics given by Fabre [J. Phys. (France) 50, 1209 (1989)].

Patent
07 Nov 2006
TL;DR: In this article, an optical image measuring instrument capable of shorting the measurement time is presented. But the measurement of the object is performed using two polarized components (L1, L2) of the interference light.
Abstract: An optical image measuring instrument capable of shorting the measurement time. A flash is outputted from a xenon lamp (2) and converted into a wide-band light by means of an optical filter (2A). The flash is converted into a linearly polarized light by means of a polarizing plate (3). The linearly polarized light is divided into a signal light (S) and a reference light (R) by means of a semitransparent mirror (6). The reference light (R) is converted into a circularly polarized light by means of a wavelength plate (7). The signal light (S) and the reference light (R) are combined by means of a semitransparent mirror (6) to produce an interference light (L). A CCD (23) detects the interference light having the same characteristic as the interference light (L). The interference light (L) is separated into an S-polarized component (L1) and a P-polarized component (L2) by means of a polarized beam splitter (11). These components are detected by means of CCDs (21, 22). A computer (30) creates an image of an object (O) to be measured from the detection signals from the CCDs (21, 22, 23). With such an optical image measuring instrument (1), since two polarized components (L1, L2) of the interference light (L) can be simultaneously obtained, the measurement time can be shortened.

Patent
30 Mar 2006
TL;DR: In this article, a light emitting section 1 emits near-infrared coherent lights having different specific wavelengths from a light source 14 to an optical interference section 2, which transmits the incident light to the fundus oculi and reflects a part thereof to a light wavelength shifter 22.
Abstract: PROBLEM TO BE SOLVED: To provide an optical interference tomograph by which the internal state of a living body can be observed in detail using bioinformation associated with metabolism of the living body. SOLUTION: A light emitting section 1 emits near-infrared coherent lights having different specific wavelengths from a light source 14 to an optical interference section 2. A beam splitter 21 of the optical interference section 2 transmits the incident light to the fundus oculi and reflects a part thereof to a light wavelength shifter 22. The shifter 22 modulates the frequency of the light according to an oscillation signal S, and re-modulates the frequency of the light reflected by a movable mirror 24. The beam splitter 21 interferences the measurement light reflected at the fundus oculi with a reference light reflected by the mirror 22 and emits the interference light to a photodetection section 3. When receiving the interference light, the photodetection section 3 demodulates the detection signal indicating the intensity of the interference light using the oscillation signal S and filters high-frequency components. The photodetection section 3 calculates the cross sectional shape of the fundus oculi and the oxygen saturation SO 2 using the detection signal. COPYRIGHT: (C)2008,JPO&INPIT

Journal ArticleDOI
TL;DR: A three-core polarization splitter based on a square-lattice photonic-crystal fiber is presented, which separates the input field into two orthogonally polarized beams that are coupled to the horizontal and vertical output ports.
Abstract: A three-core polarization splitter based on a square-lattice photonic-crystal fiber is presented. The component separates the input field into two orthogonally polarized beams that are coupled to the horizontal and vertical output ports. The splitter has been designed through modal and beam propagation analysis by employing high-performance codes based on the finite-element method. Results obtained for a device length of 20 mm show extinction ratios as low as −23 dB with bandwidths as great as 90 nm.

Journal ArticleDOI
TL;DR: A white-light spectral interferometric technique for measuring the absolute spectral optical path difference (OPD) between the beams in a slightly dispersive Michelson interferometer with a thin-film structure as a mirror is presented.
Abstract: We present a white-light spectral interferometric technique for measuring the absolute spectral optical path difference (OPD) between the beams in a slightly dispersive Michelson interferometer with a thin-film structure as a mirror. We record two spectral interferograms to obtain the spectral interference signal and retrieve from it the spectral phase, which includes the effect of a cube beam splitter and the phase change on reflection from the thin-film structure. Knowing the effective thickness and dispersion of the beam splitter made of BK7 optical glass, we use a simple procedure to determine both the absolute spectral phase difference and OPD. The spectral OPD is measured for a uniform SiO2 thin film on a silicon wafer and is fitted to the theoretical spectral OPD to obtain the thin-film thickness. The theoretical spectral OPD is determined provided that the optical constants of the thin-film structure are known. We measure also the nonlinear-like spectral phase and fit it to the theoretical values in order to obtain the thin-film thickness.

Journal ArticleDOI
TL;DR: In this article, a polarization-insensitive 1 × 2 multimode interference beam splitter based on sandwiched structures is proposed and investigated theoretically for the components of ultrasmall optical integrated circuits.
Abstract: A polarization-insensitive 1times2 multimode interference beam splitter based on sandwiched structures is proposed and investigated theoretically for the components of ultrasmall optical integrated circuits. Strong polarization dependencies arising in Si-wire waveguide systems are compensated by introducing sandwiched structures

Patent
31 Aug 2006
TL;DR: In this article, a plate-type polarizing beam splitter is used to reflect P-polarized range light rays and reflect Spolarised light rays from an image projector.
Abstract: In an image projector (8, 68), a light source (14) illuminates a plate-type polarizing beam splitter (40) that transmits P-polarized light rays and reflects S-polarized light rays (34). The P-polarized range light rays transmit through a green filter (841) and impinge on a first reflective LCD light valve (261). The S-polarized light rays strike a dichroic filter (48), which divides them into red and blue light rays (44, 46) that impinge on respective second and third LCD light valves (262, 263). Green light rays impinging on illuminated state pixels on the first LCD light valve are reflected with a 90° polarization change and are reflected by the polarizing beam splitter toward the projection lens. Red and blue light rays impinging on illuminated state pixels on the second and third LCD light valves are reflected with a 90° polarization change and transmit through the polarizing beam splitter toward the projection lens.

Journal ArticleDOI
TL;DR: The protocol uses two copies of phase-diffused states overlapped on a beam splitter and provides Gaussified, less mixed states with the degree of squeezing improved, thereby proving these optical elements can be used for successful purification of this type of state decoherence which occurs in optical transmission channels.
Abstract: We report on the first experimental demonstration of purification of nonclassical continuous variable states. The protocol uses two copies of phase-diffused states overlapped on a beam splitter and provides Gaussified, less mixed states with the degree of squeezing improved. The protocol uses only linear optical devices such as beam splitters and homodyne detection, thereby proving these optical elements can be used for successful purification of this type of state decoherence which occurs in optical transmission channels.

Journal ArticleDOI
TL;DR: In this article, a linear optical scheme was proposed for direct realization of a nondestructive $N$-qubit controlled phase gate without resorting to a sequence of single and two qubit gates.
Abstract: We propose a linear optical scheme for direct realization of a nondestructive $N$-qubit controlled phase gate without resorting to a sequence of single- and two-qubit gates. The proposed setup involves linear optical elements, nonmaximally entangled pairs of photons, and multiphoton coincidence detection. To implement the scheme, physical qubits represented by the polarization states of single photons are probabilistically encoded into the two-photon states. Based on such encoding operation, a nondestructive $N$-qubit phase gate can be directly achieved by $N$-photon interference on an array of polarization beam splitters and $N$-photon coincidence detection.

Book ChapterDOI
TL;DR: In this article, the authors discussed the nature of single-photon light fields, the interference of two photons on a beam splitter, and introduced the time-resolved two-hop interference.
Abstract: Publisher Summary This chapter discusses the nature of single-photon light fields, the interference of two photons on a beam splitter and introduces the time-resolved two-photon interference. It presents how a frequency and an emission-time jitter affect the results of a time-resolved two-photon interference experiment. On this basis, the experimental characterization of a single-photon source, based on an adiabatic passage technique, is discussed. The time-resolved two-photon interference experiments are an excellent tool to characterize single photons. In these experiments, two photons are superimposed on a beam splitter and the joint detection probability in the two output ports of the beam splitter is measured as a function of the detection-time difference of the photons. This is only possible if the photons are long compared to the detector time resolution. For identical photons, the joint detection probability is expected to be zero. Variations of the spatiotemporal modes of the photons lead to joint photo detections except for zero detection-time difference. Therefore, the joint detection probability shows a pronounced dip. From the width of this dip, one can estimate the maximum emission-time jitter and the minimum coherence time of the photons. In addition, a lower limit of the single-photon duration can be obtained. This is not possible by just measuring the average detection probability with respect to the trigger producing the photons. Moreover, the chapter shows that a frequency difference between photons leads to a distinct oscillation in the joint detection probability.

Journal ArticleDOI
TL;DR: Air hole 2D photonic crystals (PhC) and air slots have been used in association with semiconductor ridge waveguides to produce highly compact beam-splitters for power or polarization separators and mirrors.
Abstract: Air hole 2D photonic crystals (PhC) and air slots have been used in association with semiconductor ridge waveguides to produce highly compact beam-splitters (less than 10 µm×10 µm) for power or polarization separators and mirrors. An efficiency of 99% (in both 2D and 3D formulations) has been obtained for the power beam-splitter using finitedifference time-domain (FDTD) simulations-and around 95% has been measured experimentally for structures realized in silicon-on-insulator (SOI) waveguides. In the polarization splitter, an extinction ratio as large as 11 dB was also reached experimentally. Examples of combinations of these elements in the form of interferometers are also presented.