arXiv subjects

Yaron Silberberg

Publications and source records attributed to Yaron Silberberg.

54 records · Page 3Linked to original sources

arXiv2009

Scalable generation of multiphoton path entanglement with high NOON-state fidelity

"Schrodinger's cat" is a gedankenexperiment intended to highlight conceptual difficulties in the interpretation of quantum mechanics. The generation of 'cat-like' states is central to numerous quantum information protocols. In particular, much attention has been drawn by states containing N photons in a superposition of all being in one of two designated modes. These maximally path entangled states, known as 'NOON' states, exhibit enhanced phase sensitivity and allow reaching the fundamental quantum limit of precision measurement. Such states could also be used for obtaining 'super-resolution' in quantum lithography. Creation of NOON states in the lab, has been limited to N=3. Surpassing this has proven a formidable experimental challenge. Here, we realize a scheme for generation of high fidelity NOON states with arbitrarily large N. We demonstrate the versatility of the scheme by measuring up to N=5 in a single setup, this is in contrast to previous experiments which were custom-designed for a specific N. The scheme is based on high order interference between 'quantum' down-converted light and 'classical' coherent light in the photon number basis. Our results verify the high degree of path entanglement which emerges naturally from the interference of two ubiquitous, easy to generate, states of light.

quant-ph↗

arXiv2009

Compressive ghost imaging

We describe an advanced image reconstruction algorithm for pseudothermal ghost imaging, reducing the number of measurements required for image recovery by an order of magnitude. The algorithm is based on compressed sensing, a technique that enables the reconstruction of an N-pixel image from much less than N measurements. We demonstrate the algorithm using experimental data from a pseudothermal ghost-imaging setup. The algorithm can be applied to data taken from past pseudothermal ghost-imaging experiments, improving the reconstruction's quality.

quant-ph↗

arXiv2008

Ghost imaging with a single detector

We experimentally demonstrate pseudothermal ghost imaging and ghost diffraction using only a single single-pixel detector. We achieve this by replacing the high resolution detector of the reference beam with a computation of the propagating field, following a recent proposal by Shapiro [J. H. Shapiro, arXiv:0807.2614 (2008)]. Since only a single detector is used, this provides an experimental evidence that pseudothermal ghost imaging does not rely on non-local quantum correlations. In addition, we show the depth-resolving capability of this ghost imaging technique.

quant-ph↗

arXiv2008

Universal Correlations and Dynamic Disorder in a Nonlinear Periodic 1D System

When a periodic 1D system described by a tight-binding model is uniformly initialized with equal amplitudes at all sites, yet with completely random phases, it evolves into a thermal distribution with no spatial correlations. However, when the system is nonlinear, correlations are spontaneously formed. We find that for strong nonlinearities, the intensity histograms approach a narrow Gaussian distributed around their mean and phase correlations are formed between neighboring sites. Sites tend to be out-of-phase for a positive nonlinearity and in-phase for a negative one. The field correlations take a universal shape independent of parameters. This nonlinear evolution produces an effectively dynamically disordered potential which exhibits interesting diffusive behavior.

cond-mat.dis-nn↗

arXiv2008

Multiple Breakup of Higher-Order Spatial Solitons

The breakup of high-order spatial solitons propagating in an AlGaAs slab waveguide is studied. We experimentally observe the breakup of such beams into multiple fragments and identify the mechanism of this breakup as the combined effect of two- and three-photon-absorption. We show that the multiple breakup persists even when the value of two-photon-absorption is reduced by an order of magnitude owing to the high value of three-photon-absorption of AlGaAs at the half band-gap. The experimental results extend known mechanism of soliton breakup induced by two-photon-absorption and agree well with numerical beam propagation simulations.

physics.optics↗

arXiv2008

The effect of nonlinearity on adiabatic evolution of light

We investigate the effect of nonlinearity in a system described by an adiabatically evolving Hamiltonian. Experiments are conducted in a three-core waveguide structure that is adiabatically varying with distance, in analogy to the STIRAP process in atomic physics. In the linear regime, the system exhibits an adiabatic power transfer between two waveguides which are not directly coupled, with negligible power recorded in the intermediate coupling waveguide. In the presence of nonlinearity the behavior of this configuration is drastically altered and the adiabatic light passage is found to critically depend on the excitation power. We show how this effect is related to the destruction of the dark state formed in the STIRAP configuration.

cond-mat.other↗

arXiv2008

Geometrical Representation of Sum Frequency Generation and Adiabatic Frequency Conversion

We present a geometrical representation of sum frequency generation process in the undepleted pump approximation. The analogy of such dynamics with the known optical Bloch equations is discussed. We use this analogy to present a novel technique for the achievement of both high efficiency and large bandwidth in a sum frequency conversion processes using adiabatic inversion scheme, adapted from NMR and light-matter interaction. The adiabatic constraints are derived in this context. Last, this adiabatic frequency conversion scheme is realized experimentally by a proper design of adiabatic aperiodically poled KTP device, using quasi phased matched method. In the experiments we achieved high efficiency signal to idler conversion over a bandwidth of 140nm.

physics.optics↗

arXiv2008

Realization of quantum walks with negligible decoherence in waveguide lattices

Quantum random walks are the quantum counterpart of classical random walks, and were recently studied in the context of quantum computation. A quantum random walker is subject to self interference, leading to a remarkably different behavior than that of classical random walks such as ballistic propagation or localization due to disorder. Physical implementations of quantum walks have only been made in very small scale systems severely limited by decoherence. Here we show that the propagation of photons in waveguide lattices, which have been studied extensively in recent years, are essentially an implementation of quantum walks. Since waveguide lattices are easily constructed at large scales and display negligible decoherence, they can serve as an ideal and versatile experimental playground for the study of quantum walks and quantum algorithms. We experimentally observe quantum walks in large systems (~100 sites) and confirm quantum walks effects which were studied theoretically, including ballistic propagation, disorder and boundary related effects.

quant-ph↗

arXiv2008

Anderson localization and nonlinearity in one dimensional disordered photonic lattices

We experimentally investigate the evolution of linear and nonlinear waves in a realization of the Anderson model using disordered one dimensional waveguide lattices. Two types of localized eigenmodes, flat-phased and staggered, are directly measured. Nonlinear perturbations enhances localization in one type, and induce delocalization in the other. In a complementary approach, we study the evolution on short time scales of $δ$-like wavepackets in the presence of disorder. A transition from ballistic wavepacket expansion to exponential (Anderson) localization is observed. We find an intermediate regime in which the ballistic and localized components coexist while diffusive dynamics is absent. Evidence is found for a faster transition into localization under nonlinear conditions.

cond-mat.other↗

arXiv2007

Spectral Polarization and Spectral Phase Control of Time and Energy Entangled Photons

We demonstrate a scheme to spectrally manipulate a collinear, continuous stream of time and energy entangled photons to generate beamlike, bandwidth-limited fuxes of polarization-entangled photons with nearly-degenerate wavelengths. Utilizing an ultrashort-pulse shaper to control the spectral phase and polarization of the photon pairs, we tailor the shape of the Hong-Ou-Mandel interference pattern, demonstrating the rules that govern the dependence of this interference pattern on the spectral phases of the photons. We then use the pulse shaper to generate all four polarization Bell states. The singlet state generated by this scheme forms a very robust decoherence-free subspace, extremely suitable for long distance fiber-optics based quantum communication.

quant-ph↗

arXiv2006

Design of a High Power Continuous Source of Broadband Down-Converted Light

We present the design and experimental proof of principle of a low threshold optical parametric oscillator (OPO) that continuously oscillates over a large bandwidth allowed by phase matching. The large oscillation bandwidth is achieved with a selective two-photon loss that suppresses the inherent mode competition, which tends to narrow the bandwidth in conventional OPOs. Our design performs pairwise mode-locking of many frequency pairs, in direct equivalence to passive mode-locking of ultrashort pulsed lasers. The ability to obtain high powers of continuous \textit{and} broadband down-converted light enables the optimal exploitation of the correlations within the down-converted spectrum, thereby strongly affecting two-photon interactions even at classically high power levels, and opening new venues for applications such as two-photon spectroscopy and microscopy and optical spread spectrum communication.

quant-ph↗

arXiv2004

Nonlinear interactions with an ultrahigh flux of broadband entangled photons

We experimentally demonstrate sum-frequency generation (SFG) with entangled photon-pairs, generating as many as 40,000 SFG photons per second, visible even to the naked eye. The nonclassical nature of the interaction is exhibited by a linear intensity-dependence of the nonlinear process. The key element in our scheme is the generation of an ultrahigh flux of entangled photons while maintaining their nonclassical properties. This is made possible by generating the down-converted photons as broadband as possible, orders of magnitude wider than the pump. This approach is readily applicable for other nonlinear interactions, and may be applicable for various quantum-measurement tasks.

quant-ph↗

arXiv2004

Temporal shaping of entangled photons

We experimentally demonstrate shaping of the two-photon wavefunction of entangled photon-pairs, utilizing coherent pulse-shaping techniques. By performing spectral-phase manipulations we tailor the two-photon wavefunction exactly like a coherent ultrashort pulse. To observe the shaping we perform sum-frequency generation (SFG) with an ultrahigh flux of entangled photons. At the appropriate conditions, SFG performs as a coincidence detector with an ultrashort response time (~100 fs), enabling a direct observation of the two-photon wavefunction. This property also enables us to demonstrate background-free, high-visibility two-photon interference oscillations.

quant-ph↗

arXiv2004

Quantum lithography by coherent control of classical light pulses

The smallest spot in optical lithography and microscopy is generally limited by diffraction. Quantum lithography, which utilizes interference between groups of N entangled photons, was recently proposed to beat the diffraction limit by a factor N. Here we propose a simple method to obtain N photons interference with classical pulses that excite a narrow multiphoton transition, thus shifting the "quantum weight" from the electromagnetic field to the lithographic material. We show how a practical complete lithographic scheme can be developed and demonstrate the underlying principles experimentally by two-photon interference in atomic Rubidium, to obtain focal spots that beat the diffraction limit by a factor of 2.

quant-ph↗

arXiv2004

Observation of discrete gap solitons in binary waveguide arrays

We report on the first experimental observation of discrete gap solitons in binary arrays of optical waveguides. We observe the soliton generation when the inclination angle of an input beam is slightly above the Bragg angle, and show that the propagation direction of the emerging gap soliton depends on the input power as a result of an inter-band momentum exchange.

physics.optics↗

arXiv2004

Two photon absorption and coherent control with broadband down-converted light

We experimentally demonstrate two-photon absorption (TPA) with broadband down-converted light (squeezed vacuum). Although incoherent and exhibiting the statistics of a thermal noise, broadband down-converted light can induce TPA with the same sharp temporal behavior as femtosecond pulses, while exhibiting the high spectral resolution of the narrowband pump laser. Using pulse-shaping methods, we coherently control TPA in Rubidium, demonstrating spectral and temporal resolutions that are 3-5 orders of magnitude below the actual bandwidth and temporal duration of the light itself. Such properties can be exploited in various applications such as spread-spectrum optical communications, tomography and nonlinear microscopy.

quant-ph↗

arXiv2003

Coherent control with broadband squeezed vacuum

We report the experimental demonstration of coherent control with high power, broadband squeezed vacuum. Although incoherent and exhibiting the statistics of a thermal noise, broadband squeezed vacuum is shown to induce certain two-photon interactions as a coherent ultrashort pulse with the same spectral bandwidth. Utilizing pulse-shaping techniques we coherently control the sum-frequency generation of broadband squeezed vacuum over a range of two orders of magnitude. Coherent control of two-photon interactions with broadband squeezed vacuum can potentially obtain spectral resolutions and extinction ratios that are practically unattainable with coherent pulses.

quant-ph↗

arXiv2003

Transform-limited pulses are not optimal for resonant multiphoton transitions

Maximizing nonlinear light-matter interactions is a primary motive for compressing laser pulses to achieve ultrashort transform limited pulses. Here we show how, by appropriately shaping the pulses, resonant multiphoton transitions can be enhanced significantly beyond the level achieved by maximizing the pulse's peak intensity. We demonstrate the counterintuitive nature of this effect with an experiment in a resonant two-photon absorption, in which, by selectively removing certain spectral bands, the peak intensity of the pulse is reduced by a factor of 40, yet the absorption rate is doubled. Furthermore, by suitably designing the spectral phase of the pulse, we increase the absorption rate by a factor of 7.

physics.atom-ph↗