Quantum-optical state engineering up to the two-photon level (original) (raw)
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Quantum State Engineering of Light with Continuous-wave Optical Parametric Oscillators
Journal of Visualized Experiments, 2014
The ability to engineer the quantum state of traveling optical fields is a central requirement for quantum information science and technology, including quantum communication, computing and metrology. In this video article, we describe the reliable generation of non-Gaussian states, including single-photon states and coherent state superpositions, using a conditional preparation method operated on the non-classical light emitted by optical parametric oscillators. Type-I and type-II phase-matched OPOs operated below threshold, i.e. single-mode or two-mode squeezed vacuum sources, are considered and common procedures, such as the required frequency filtering or the high-efficiency quantum state characterization by homodyning, are detailed. The reported method enables a high fidelity with the targeted state and the generation of the state in a well-controlled spatiotemporal mode, a crucial feature for their use in subsequent protocols.
Optics Communications, 2014
Quantum optics experiments frequently involve interfering single photons and coherent states. In the case of multi-photon experiments this requires that all photons are frequency degenerate. We report a simple and practical approach to generate coherent states that can be readily tuned to any wavelength required, for example by non-degenerate photon pair creation. We demonstrate this by performing a two-photon (Hong-Ou-Mandel) interference experiment between a coherent state and a pure heralded single photon source. No spectral filtering is required on either source, the coherent state constrained by the pump and seed lasers and the heralded photon exploits non-local filtering. We expect that such an approach can find a wide range of applications in photonic based quantum information science.
Quantum state engineering via coherent-state superpositions in traveling optical fields
Physical review, 2018
We propose two experimental schemes for producing coherent-state superpositions which approximate different nonclassical states conditionally in traveling optical fields. Although these setups are constructed of a small number of linear optical elements and homodyne measurements, they can be used to generate various photon number superpositions in which the number of constituent states can be higher than the number of measurements in the schemes. We determine numerically the parameters to achieve maximal fidelity of the preparation for a large variety of nonclassical states, such as amplitude squeezed states, squeezed number states, binomial states and various photon number superpositions. The proposed setups can generate these states with high fidelities and with success probabilities that can be promising for practical applications.
Single-photon two-qubit entangled states: Preparation and measurement
Physical Review A, 2003
We implement experimentally a deterministic method to prepare and measure so called singlephoton two-qubit entangled states or single-photon Bell-states, in which the polarization and the spatial modes of a single-photon each represent a quantum bit. All four single-photon Bell-states can be easily prepared and measured deterministically using linear optical elements alone. We also discuss how this method can be used for recently proposed single-photon two-qubit quantum cryptography protocol.
Experimental Two‐Way Communication with One Photon
Advanced Quantum Technologies, 2019
Superposition of two or more states is one of the fundamental concepts of quantum mechanics and provides the basis for several advantages offered by quantum information processing. In this work, we experimentally demonstrate that quantum superposition allows for two-way communication between two distant parties that can exchange only one particle once, an impossible task in classical physics. This is achieved by preparing a single photon in a coherent superposition of the two parties' locations. Furthermore, we show that this concept allows the parties to perform secure and anonymous quantum communication employing one particle per transmitted bit. These important features can lead to the realization of new quantum communication schemes, which are simultaneously anonymous, secure and resource-efficient.
Physical Review Letters, 2003
We report the first experimental demonstration of conditional preparation of a non-classical state of light in the continuous variable regime. Starting from a non-degenerate OPO which generates above threshold quantum intensity correlated signal and idler "twin beams", we keep the recorded values of the signal intensity only when the idler intensity falls inside a band of values narrower than its standard deviation. By this very simple technique, we generate a sub-Poissonian state 4.4 dB (64%) below shot noise from twin beams exhibiting 7.5 dB (82%) of noise reduction in the intensity difference. PACS numbers: 42.50 Dv, 42.65.Yj A well-known technique to generate a single photon state from quantum correlated photons ("twin photons") is to use the method of conditional measurement: if one labels and the two modes in which the twin photons are emitted, it consists in retaining in the information collected on mode (1) only the counts occurring when a photon is detected in mode (2) (within a given time window ∆T ). This method has been widely and very successfully used over the past decades, firstly with twin photons generated by an atomic cascade [1], then by using the more efficient technique of parametric down conversion . Various protocols have been proposed to use conditional preparation in order to generate other kinds of non-classical states, for example Schrödinger cat states using a squeezed vacuum state transmitted through a beamsplitter and a measurement conditioned by the counts detected on the reflected port . In a similar way, teleportation of a quantum state of light can be achieved by using conditional measurements [4] and the degree of entanglement can be improved by photon subtractions . In cavity QED, conditional measurements on the atomic state have also led to the experimental generation of non-classical photon states [6].
Quantum information processing and precise optical measurement with entangled-photon pairs
Contemporary Physics, 2003
Two photons in a pair generated in the nonlinear optical process of spontaneous parametric down-conversion are, in general, strongly quantum entangled. Accordingly, they contain extremely strong energy, time, polarization and momentum quantum correlations. This entanglement involves more than one quantum variable and has served as a powerful tool in fundamental studies of quantum theory. It is now playing a large role in the development of novel information processing techniques and new optical measurement technologies. Here we review some of these technologies and their origins.
Optics Express, 2010
We propose and provide experimental evidence in support of a theory for the remote preparation of a complex spatial state of a single photon. An entangled two-photon source was obtained by spontaneous parametric down-conversion, and a double slit was placed in the path of the signal photon as a scattering object. The signal photon was detected after proper spatial filtering so that the idler photon was prepared in the corresponding single-photon state. By using a two-photon coincidence measurement, we obtained the Radon transform, at several longitudinal distances, of the single-photon Wigner distribution function modified by the double slit. The experimental results are consistent with the idler photon being in a pure state. An inverse Radon transformation can, in principle, be applied to the measured data to reconstruct the modified single-photon Wigner function, which is a complete representation of the amplitude and phase structure of the scattering object.