Showing papers on "Interferometry published in 2013"
TL;DR: In this article, the authors describe the detailed design of the KAGRA interferometer as well as the reasoning behind the design choices, including the length and alignment sensing schemes for the robust control of the inter-ferometer.
Abstract: KAGRA is a cryogenic interferometric gravitational-wave detector being constructed at the underground
site of Kamioka mine in Gifu prefecture, Japan. We performed an optimization of the interferomter
design, to achieve the best sensitivity and a stable operation, with boundary conditions of classical
noises and under various practical constraints, such as the size of the tunnel or the mirror cooling capacity.
Length and alignment sensing schemes for the robust control of the interferometer are developed. In this
paper, we describe the detailed design of the KAGRA interferometer as well as the reasoning behind
design choices.
846 citations
TL;DR: In this article, a five-mode integrated interferometer containing three-dimensional S-bent waveguides was used to sample three single photons and the probability ratios of all events were measured.
Abstract: The boson-sampling problem was demonstrated by studying three-photon interference in a five-mode integrated interferometer containing three-dimensional S-bent waveguides. Three single photons were input into the interferometer and the probability ratios of all events were measured. The results agree with quantum mechanical predictions for three-photon interference.
668 citations
TL;DR: In this article, direct-bonded monocrystalline multilayers are used for optical interferometry, which exhibit both intrinsically low mechanical loss and high optical quality.
Abstract: Thermally induced fluctuations impose a fundamental limit on precision measurement. In optical interferometry, the current bounds of stability and sensitivity are dictated by the excess mechanical damping of the high-reflectivity coatings that comprise the cavity end mirrors. Over the last decade, the dissipation of these amorphous multilayer reflectors has at best been reduced by a factor of two. Here, we demonstrate a new paradigm in optical coating technology based on directbonded monocrystalline multilayers, which exhibit both intrinsically low mechanical loss and high optical quality.
355 citations
TL;DR: A miniaturized and robust experiment within the QUANTUS collaboration using ultra cold atoms in a free fall environment as a test-bed for matter-wave interferometry on long timescales is reported on.
Abstract: Atom interferometers covering macroscopic domains of space-time are a spectacular manifestation of the wave nature of matter. Because of their unique coherence properties, Bose-Einstein condensates are ideal sources for an atom interferometer in extended free fall. In this Letter we report on the realization of an asymmetric Mach-Zehnder interferometer operated with a Bose-Einstein condensate in microgravity. The resulting interference pattern is similar to the one in the far field of a double slit and shows a linear scaling with the time the wave packets expand. We employ delta-kick cooling in order to enhance the signal and extend our atom interferometer. Our experiments demonstrate the high potential of interferometers operated with quantum gases for probing the fundamental concepts of quantum mechanics and general relativity.
330 citations
TL;DR: New ways of making low-noise beams of light could lead to more sensitive optical interferometry measurements as mentioned in this paper. But these methods require a large amount of power and are not suitable for outdoor use.
Abstract: New ways of making low-noise beams of light could lead to more sensitive optical interferometry measurements.
268 citations
TL;DR: In this paper, a new detection strategy based on recent advances in optical atomic clocks and atom interferometry which can operate at long baselines and which is immune to laser frequency noise is proposed.
Abstract: Laser frequency noise is a dominant noise background for the detection of gravitational waves using long-baseline optical interferometry. Amelioration of this noise requires near simultaneous strain measurements on more than one interferometer baseline, necessitating, for example, more than two satellites for a space-based detector or two interferometer arms for a ground-based detector. We describe a new detection strategy based on recent advances in optical atomic clocks and atom interferometry which can operate at long baselines and which is immune to laser frequency noise. Laser frequency noise is suppressed because the signal arises strictly from the light propagation time between two ensembles of atoms. This new class of sensor allows sensitive gravitational wave detection with only a single baseline. This approach also has practical applications in, for example, the development of ultrasensitive gravimeters and gravity gradiometers.
227 citations
TL;DR: A full Mach-Zehnder sequence with trapped Bose-Einstein condensates confined on an atom chip is demonstrated, highlighting the potential of entanglement as a resource for metrology and paving the way for integrated quantum-enhanced matter-wave sensors.
Abstract: Particle-wave duality enables the construction of interferometers for matter waves, which complement optical interferometers in precision measurement devices. This requires the development of atom-optics analogues to beam splitters, phase shifters and recombiners. Integrating these elements into a single device has been a long-standing goal. Here we demonstrate a full Mach-Zehnder sequence with trapped Bose-Einstein condensates confined on an atom chip. Particle interactions in our Bose-Einstein condensate matter waves lead to a nonlinearity, absent in photon optics. We exploit it to generate a non-classical state having reduced number fluctuations inside the interferometer. Making use of spatially separated wave packets, a controlled phase shift is applied and read out by a non-adiabatic matter-wave recombiner. We demonstrate coherence times a factor of three beyond what is expected for coherent states, highlighting the potential of entanglement as a resource for metrology. Our results pave the way for integrated quantum-enhanced matter-wave sensors.
218 citations
TL;DR: This work proposes to use an optically levitated diamond bead containing a nitrogen-vacancy center spin to show how the interference between spatially separated states of the center of mass of a mesoscopic harmonic oscillator can be evidenced by coupling it to a spin and performing solely spin manipulations and measurements (Ramsey interferometry).
Abstract: We show how the interference between spatially separated states of the center of mass (c.m.) of a mesoscopic harmonic oscillator can be evidenced by coupling it to a spin and performing solely spin manipulations and measurements (Ramsey interferometry). We propose to use an optically levitated diamond bead containing a nitrogen-vacancy center spin. The nanoscale size of the bead makes the motional decoherence due to levitation negligible. The form of the spin-motion coupling ensures that the scheme works for thermal states so that moderate feedback cooling suffices. No separate control or observation of the c.m. state is required and thereby one dispenses with cavities, spatially resolved detection, and low-mass-dispersion ensembles. The controllable relative phase in the Ramsey interferometry stems from a gravitational potential difference so that it uniquely evidences coherence between states which involve the whole nanocrystal being in spatially distinct locations.
169 citations
TL;DR: This work significantly advances the technology of electromagnetically induced transparency-based optical memory and may find practical applications in long-distance quantum communication and optical quantum computation.
Abstract: A high-storage efficiency and long-lived quantum memory for photons is an essential component in long-distance quantum communication and optical quantum computation. Here, we report a 78% storage efficiency of light pulses in a cold atomic medium based on the effect of electromagnetically induced transparency. At 50% storage efficiency, we obtain a fractional delay of 74, which is the best up-to-date record. The classical fidelity of the recalled pulse is better than 90% and nearly independent of the storage time, as confirmed by the direct measurement of phase evolution of the output light pulse with a beat-note interferometer. Such excellent phase coherence between the stored and recalled light pulses suggests that the current result may be readily applied to single photon wave packets. Our work significantly advances the technology of electromagnetically induced transparency-based optical memory and may find practical applications in long-distance quantum communication and optical quantum computation.
165 citations
TL;DR: This work uses a small Bose-Einstein condensate on an atom chip as an interferometric scanning probe to map out a microwave field near the chip surface with a few micrometers resolution and overcomes the standard quantum limit of interferometry.
Abstract: Atom interferometers provide record precision in measurements of a broad range of physical quantities. Extending atom interferometry to micrometer spatial resolution would enable new applications in electromagnetic field sensing, surface science, and the search for fundamental short-range interactions. I present experiments where we use a small Bose-Einstein condensate on an atom chip as an interferometric scanning probe to map out a microwave field at distances down to $16$ micrometer from the chip surface with a few micrometers spatial resolution. By creating entanglement between the atoms, our interferometer overcomes the standard quantum limit of interferometry by 4 dB in variance and maintains enhanced performance for interrogation times up to 10 ms. This corresponds to a microwave magnetic field sensitivity of 77 pT/sqrt(Hz) in a probe volume of 20 cubic micrometer. High-resolution measurements of microwave near-fields, as demonstrated here, are important for the development of integrated microwave circuits for quantum information processing and applications in communication technology.
Quantum metrology with entangled atoms is particularly useful in measurements with high spatial resolution, since the atom number in the probe volume is limited by collisional losses. I analyze the effect of such density-dependent losses in high-resolution atom interferometry, and show that there is a strict upper limit on the useful number of atoms. Our experimental results indicate that even tighter limits on the particle number and interrogation time may arise from density-dependent dephasing, and provide a starting point for future studies towards the fundamental limits of coherence in Bose-Einstein condensates. Our experimental setup is ideally suited to experimentally address these questions, and provides a promising platform for further studies on quantum metrology and entanglement in many-particle atomic systems.
163 citations
TL;DR: This Letter develops a framework for digital holography at optical wavelengths by merging phase-shifting interferometry with single-pixel optical imaging based on compressive sensing by adapting the concept of a single pixel camera to perform interferometric imaging of the sampled diffraction pattern.
Abstract: This Letter develops a framework for digital holography at optical wavelengths by merging phase-shifting interferometry with single-pixel optical imaging based on compressive sensing. The field diffracted by an input object is sampled by Hadamard patterns with a liquid crystal spatial light modulator. The concept of a single-pixel camera is then adapted to perform interferometric imaging of the sampled diffraction pattern by using a Mach-Zehnder interferometer. Phase-shifting techniques together with the application of a backward light propagation algorithm allow the complex amplitude of the object under scrutiny to be resolved. A proof-of-concept experiment evaluating the phase distribution of an ophthalmic lens with compressive phase-shifting holography is provided.
TL;DR: A simple-to-align, highly-portable interferometer, which is able to capture wide-field, off-axis interference patterns from transparent samples under low-coherence illumination and enables to easily obtain high-quality quantitative images of static and dynamic samples is presented.
Abstract: We present a simple-to-align, highly-portable interferometer, which is able to capture wide-field, off-axis interference patterns from transparent samples under low-coherence illumination. This small-dimensions and low-cost device can be connected to the output of a transmission microscope illuminated by a low-coherence source and measure sub-nanometric optical thickness changes in a label-free manner. In contrast to our previously published design, the τ interferometer, the new design is able to fully operate in an off-axis holographic geometry, where the interference fringes have high spatial frequency, and the interference area is limited only by the coherence length of the source, and thus it enables to easily obtain high-quality quantitative images of static and dynamic samples. We present several applications for the new design including nondestructive optical testing of transparent microscopic elements with nanometric thickness and live-cell imaging.
TL;DR: A distributed optical fiber sensing system merged Mach-Zehnder interferometer and phase sensitive optical time domain reflectometer system for vibration measurement with high-frequency response and high spatial resolution is demonstrated, where modulated pulses are proposed to be used as sensing source.
Abstract: A distributed optical fiber sensing system merged Mach-Zehnder interferometer and phase sensitive optical time domain reflectometer (φ-OTDR) system for vibration measurement with high-frequency response and high spatial resolution is demonstrated, where modulated pulses are proposed to be used as sensing source. Frequency response and location information are obtained by Mach-Zehnder interferometer and φ-OTDR technology, respectively. In order to simulate high-frequency vibration of crack of cable and civil structure, experiments on detection of piezoelectric transducer and pencil-break are carried out. Spatial resolution of 5 m and the maximum frequency response of ~3 MHz are achieved in 1064 m fiber link when the narrow pulse width is 50 ns.
TL;DR: This work presents a simple and robust digital optical phase conjugation (DOPC) implementation for suppressing multiple light scattering, and demonstrates its turbidity-suppression capability by reconstructing the image of a complex two-dimensional wide-field target through a highly scattering medium.
Abstract: Optical transmission through complex media such as biological tissue is fundamentally limited by multiple light scattering. Precise control of the optical wavefield potentially holds the key to advancing a broad range of light-based techniques and applications for imaging or optical delivery. We present a simple and robust digital optical phase conjugation (DOPC) implementation for suppressing multiple light scattering. Utilizing wavefront shaping via a spatial light modulator (SLM), we demonstrate its turbidity-suppression capability by reconstructing the image of a complex two-dimensional wide-field target through a highly scattering medium. Employing an interferometer with a Sagnac-like ring design, we successfully overcome the challenging alignment and wavefront-matching constraints in DOPC, reflecting the requirement that the forward- and reverse-propagation paths through the turbid medium be identical. By measuring the output response to digital distortion of the SLM write pattern, we validate the sub-wavelength sensitivity of the system.
German Aerospace Center1, Leibniz University of Hanover2, University of Bordeaux3, Ferdinand-Braun-Institut4, University of Zurich5, University of Birmingham6, University of Bremen7, European Space Agency8, Dornier Flugzeugwerke9, Institut de Ciències de l'Espai10, Humboldt University of Berlin11, University of Hamburg12, Centre National D'Etudes Spatiales13, University of Ulm14, University of Florence15, National Technical University of Athens16, Foundation for Research & Technology – Hellas17, Technische Universität Darmstadt18, Office National d'Études et de Recherches Aérospatiales19
TL;DR: The STE-QUEST satellite mission as mentioned in this paper is a medium-size mission within the Cosmic Vision program of the European Space Agency (ESA), which aims to test general relativity with high precision in two experiments by performing a measurement of the gravitational redshift of the Sun and the Moon by comparing terrestrial clocks, and by comparing the trajectories of two Bose-Einstein condensates of Rb85 and Rb87.
Abstract: The theory of general relativity describes macroscopic phenomena driven by the influence of gravity while quantum mechanics brilliantly accounts for microscopic effects. Despite their tremendous individual success, a complete unification of fundamental interactions is missing and remains one of the most challenging and important quests in modern theoretical physics. The STE-QUEST satellite mission, proposed as a medium-size mission within the Cosmic Vision program of the European Space Agency (ESA), aims for testing general relativity with high precision in two experiments by performing a measurement of the gravitational redshift of the Sun and the Moon by comparing terrestrial clocks, and by performing a test of the Universality of Free Fall of matter waves in the gravitational field of Earth comparing the trajectory of two Bose-Einstein condensates of Rb85 and Rb87. The two ultracold atom clouds are monitored very precisely thanks to techniques of atom interferometry. This allows to reach down to an uncertainty in the Eotvos parameter of at least 2x10E-15. In this paper, we report about the results of the phase A mission study of the atom interferometer instrument covering the description of the main payload elements, the atomic source concept, and the systematic error sources.
TL;DR: In this paper, a monostatic radar based on a six-port interferometer operating a continuous-wave signal at 24 GHz and a radiated power of less than 3 GHz is presented.
Abstract: A novel remote respiration and heartbeat monitoring sensor is presented The device is a monostatic radar based on a six-port interferometer operating a continuous-wave signal at 24 GHz and a radiated power of less than 3 $\mu\hbox{W}$ Minor mechanical movements of the patient's body caused by the respiration as well as hearbeat can be tracked by analyzing the phase modulation of the backscattered signal by means of microwave interferometry with the six-port network High-distance measurement accuracy in the micrometer scale as well as low system complexity are the benefits of the six-port receiver To verify the performance of the system, different body areas have been observed by the six-port radar The proposed system has been tested and validated by measurement results
TL;DR: In this paper, the authors theoretically show that the recently reported quantum-noise-limited sensitivity of the squeezed-lightenhanced German-British gravitational wave detector GEO 600 is exceedingly close to this bound, given the present amount of optical loss.
Abstract: The fundamental quantum interferometry bound limits the sensitivity of an interferometer for a given total rate of photons and for a given decoherence rate inside the measurement device. We theoretically show that the recently reported quantum-noise-limited sensitivity of the squeezed-light-enhanced German-British gravitational wave detector GEO 600 is exceedingly close to this bound, given the present amount of optical loss. Furthermore, our result proves that the employed combination of a bright coherent state and a squeezed vacuum state is generally the optimum practical approach for phase estimation with high precision on absolute scales. Based on our analysis we conclude that the application of neither Fock states nor NOON states nor any other sophisticated nonclassical quantum state would have yielded an appreciably higher quantum-noise-limited sensitivity.
TL;DR: This work demonstrates experimentally the key influence of the steepness of the plasma-vacuum interface on the interaction, by measuring the spectral and spatial properties of harmonics generated on a plasma mirror whose initial density gradient scale length L is continuously varied.
Abstract: High-order harmonics and attosecond pulses of light can be generated when ultraintense, ultrashort laser pulses reflect off a solid-density plasma with a sharp vacuum interface, i.e., a plasma mirror. We demonstrate experimentally the key influence of the steepness of the plasma-vacuum interface on the interaction, by measuring the spectral and spatial properties of harmonics generated on a plasma mirror whose initial density gradient scale length L is continuously varied. Time-resolved interferometry is used to separately measure this scale length.
TL;DR: The question is what is the best state to inject into the second input port, given a constraint on the mean number of photons this state can carry, in order to optimize the interferometer's phase sensitivity?
Abstract: We consider an interferometer powered by laser light (a coherent state) into one input port and ask the following question: what is the best state to inject into the second input port, given a constraint on the mean number of photons this state can carry, in order to optimize the interferometer’s phase sensitivity? This question is the practical question for high-sensitivity interferometry. We answer the question by considering the quantum Cramer-Rao bound for such a setup. The answer is squeezed vacuum.
TL;DR: A stationary Fourier-transform spectrometer chip implemented in silicon microphotonic waveguides with phase and amplitude errors arising from fabrication imperfections compensated using a transformation matrix spectral retrieval algorithm is reported.
Abstract: We report a stationary Fourier-transform spectrometer chip implemented in silicon microphotonic waveguides. The device comprises an array of 32 Mach-Zehnder interferometers (MZIs) with linearly increasing optical path delays between the MZI arms across the array. The optical delays are achieved by using Si-wire waveguides arranged in tightly coiled spirals with a compact device footprint of 12 mm(2). Spectral retrieval is demonstrated in a single measurement of the stationary spatial interferogram formed at the output waveguides of the array, with a wavelength resolution of 40 pm within a free spectral range of 0.75 nm. The phase and amplitude errors arising from fabrication imperfections are compensated using a transformation matrix spectral retrieval algorithm.
TL;DR: In this paper, a precision gravimeter based on coherent Bragg diffraction of freely falling cold atoms is presented. But it is not suitable for beamforming and subsequent separation of momentum states for detection due to the inherently multi-state nature of atom diffraction.
Abstract: We present a precision gravimeter based on coherent Bragg diffraction of freely falling cold atoms. Traditionally, atomic gravimeters have used stimulated Raman transitions to separate clouds in momentum space by driving transitions between two internal atomic states. Bragg interferometers utilize only a single internal state, and can therefore be less susceptible to environmental perturbations. Here we show that atoms extracted from a magneto-optical trap using an accelerating optical lattice are a suitable source for a Bragg atom interferometer, allowing efficient beamsplitting and subsequent separation of momentum states for detection. Despite the inherently multi-state nature of atom diffraction, we are able to build a Mach-Zehnder interferometer using Bragg scattering which achieves a sensitivity to the gravitational acceleration of Δg/g = 2.7 × 10-9 with an integration time of 1000 s. The device can also be converted to a gravity gradiometer by a simple modification of the light pulse sequence.
TL;DR: An elegant way of achieving an ultracompact optical fiber in-line Mach-Zehnder interferometer is to create an inner air cavity in a section of microfiber that splits the light propagating in the fiber into two beams, resulting in an interference fringe pattern.
Abstract: An elegant way of achieving an ultracompact optical fiber in-line Mach–Zehnder interferometer is to create an inner air cavity in a section of microfiber. The sandwich structure splits the light propagating in the fiber into two beams: one passes through the inner air cavity and the other travels along the silica wall of the cavity before recombining at the cavity end, resulting in an interference fringe pattern. Such a device is applied for strain measurement with a high sensitivity of 6.8 pm/μe.
TL;DR: In this article, the authors demonstrate phase sensitivity in a horizontally guided, acceleration-sensitive atom interferometer with a momentum separation of $80\ensuremath{hbar}k$ between its arms.
Abstract: We demonstrate phase sensitivity in a horizontally guided, acceleration-sensitive atom interferometer with a momentum separation of $80\ensuremath{\hbar}k$ between its arms. A fringe visibility of 7% is observed. Our coherent pulse sequence accelerates the cold cloud in an optical waveguide, an inherently scalable route to large momentum separation and high sensitivity. We maintain coherence at high momentum separation due to both the transverse confinement provided by the guide and our use of optical $\ensuremath{\delta}$-kick cooling on our cold-atom cloud. We also construct a horizontal interferometric gradiometer to measure the longitudinal curvature of our optical waveguide.
TL;DR: A sub-aperture correlation based numerical phase correction method for interferometric full field imaging systems provided the complex object field information can be extracted without the need of any adaptive optics, spatial light modulators (SLM) and additional cameras.
Abstract: This paper proposes a sub-aperture correlation based numerical phase correction method for interferometric full field imaging systems provided the complex object field information can be extracted. This method corrects for the wavefront aberration at the pupil/ Fourier transform plane without the need of any adaptive optics, spatial light modulators (SLM) and additional cameras. We show that this method does not require the knowledge of any system parameters. In the simulation study, we consider a full field swept source OCT (FF SSOCT) system to show the working principle of the algorithm. Experimental results are presented for a technical and biological sample to demonstrate the proof of the principle.
TL;DR: This work demonstrates an interferometric scheme combined with a time-domain analysis to measure longitudinal velocities and shows the estimator to be efficient by reaching its Cramér-Rao bound.
Abstract: In a recent Letter, Brunner and Simon proposed an interferometric scheme using imaginary weak values with a frequency-domain analysis to outperform standard interferometry in longitudinal phase shifts [Phys. Rev. Lett105, 010405 (2010)]. Here we demonstrate an interferometric scheme combined with a time-domain analysis to measure longitudinal velocities. The technique employs the near-destructive interference of non-Fourier limited pulses, one Doppler shifted due to a moving mirror in a Michelson interferometer. We achieve a velocity measurement of 400 fm/s and show our estimator to be efficient by reaching its Cramer-Rao bound.
TL;DR: In this article, the authors show that by stacking ambient-noise cross-correlations between USArray seismometers, body wave phases reflected off the outer core (ScS) and twice refracted through the inner core (PKIKP^2) can be clearly extracted.
Abstract: Seismic body waves that sample Earth's core are indispensable for studying the most remote regions of the planet. Traditional core phase studies rely on well-defined earthquake signals, which are spatially and temporally limited. We show that, by stacking ambient-noise cross-correlations between USArray seismometers, body wave phases reflected off the outer core (ScS), and twice refracted through the inner core (PKIKP^2) can be clearly extracted. Temporal correlation between the amplitude of these core phases and global seismicity suggests that the signals originate from distant earthquakes and emerge due to array interferometry. Similar results from a seismic array in New Zealand demonstrate that our approach is applicable in other regions and with fewer station pairs. Extraction of core phases by interferometry can significantly improve the spatial sampling of the deep Earth because the technique can be applied anywhere broadband seismic arrays exist.
TL;DR: The results indicate that EPP-2DFS can provide previously unattainable resolution to extract model Hamiltonian parameters from electronically coupled molecular dimers.
Abstract: We introduce a new method, called entangled photon-pair two-dimensional fluorescence spectroscopy (EPP-2DFS), to sensitively probe the nonlinear electronic response of molecular systems. The method incorporates a separated two-photon (‘Franson’) interferometer, which generates time-frequency-entangled photon pairs, into the framework of a fluorescence-detected 2D optical spectroscopic experiment. The entangled photons are temporally shaped and phase-modulated in the interferometer, and are used to excite a two-photon-absorbing (TPA) sample, whose excited-state population is selectively detected by simultaneously monitoring the sample fluorescence and the exciting fields. In comparison to ‘classical’ 2DFS techniques, major advantages of this scheme are the suppression of uncorrelated background signals, the enhancement of simultaneous time-and-frequency resolution, the suppression of diagonal 2D spectral features, and the enhancement and narrowing of off-diagonal spectral cross-peaks that contain informati...
TL;DR: Here it is shown that above the shot-noise limit the sensitivity of two-mode interferometers can be significantly enhanced by squeezing in input, and then measuring in output, the population fluctuations of a single mode.
Abstract: A major challenge of the phase estimation problem is the engineering of high-intensity entangled probe states. The goal is to significantly enhance above the shot-noise limit the sensitivity of two-mode interferometers. Here we show that this can be achieved by squeezing in input, and then measuring in output, the population fluctuations of a single mode. The second input mode can be left as an arbitrary nonvacuum (e.g., a bright coherent) state. This two-mode state belongs to a novel class of particle-entangled states which are not spin squeezed. Already a 2.4 db gain above shot noise can be obtained when just a single-particle Fock state is injected into the empty input port of a classical interferometer configuration. Higher gains, up to the Heisenberg limit, can be reached with squeezed states of a larger number of particles. We finally study the robustness of this protocol with respect to detection noise.
TL;DR: The experimental realization of a universal near-field interferometer built from three short-pulse single-photon ionization gratings, which is sensitive to fringe shifts as small as a few nanometers and yet robust against velocity-dependent phase shifts, since the gratings exist only for nanoseconds and form an interferometers in the time-domain.
Abstract: Matter-wave interferometry with atoms1 and molecules2 has attracted a rapidly growing interest throughout the last two decades both in demonstrations of fundamental quantum phenomena and in quantum-enhanced precision measurements. Such experiments exploit the non-classical superposition of two or more position and momentum states which are coherently split and rejoined to interfere3-11. Here, we present the experimental realization of a universal near-field interferometer built from three short-pulse single-photon ionization gratings12,13. We observe quantum interference of fast molecular clusters, with a composite de Broglie wavelength as small as 275 fm. Optical ionization gratings are largely independent of the specific internal level structure and are therefore universally applicable to different kinds of nanoparticles, ranging from atoms to clusters, molecules and nanospheres. The interferometer is sensitive to fringe shifts as small as a few nanometers and yet robust against velocity-dependent phase shifts, since the gratings exist only for nanoseconds and form an interferometer in the time-domain.
TL;DR: In this article, a laser interferometer that achieves simultaneous nonclassical readout of two conjugated observables was demonstrated, and it does not require any conditioning or post-selection.
Abstract: Researchers demonstrate a laser interferometer that achieves simultaneous nonclassical readout of two conjugated observables. Because their system uses steady-state entanglement, it does not require any conditioning or post-selection. By distinguishing between scientific and parasitic signals, its sensitivity exceeds the standard quantum limit by about 6 dB.