We investigate the efficiency of atom-cavity based photon-generation schemes to deliver single photons of arbitrary temporal shape. Our model applies to Raman transitions in three-level atoms with one branch of the transition driven by a laser pulse, and the other coupled to a cavity mode. For any possible shape of the single-photon wavepacket, we derive an unambiguous analytic expression for the shape of the required driving laser pulse. We furthermore discuss the constraints limiting the maximum probability for emitting any desired photon, and use these to estimate upper bounds for the efficiency of the process. The model is not only valid for Vacuum-Stimulated Raman Adiabatic Passages (V-STIRAP) in the strong-coupling and bad-cavity regime, but it generally allows controlling the coherence and population flow in any Raman process.
We present a physical scenario in which an electromagnetic field in a state consisted of photons whose energies are smaller than the energy gap of a two-state particle, interacts with the particle, for an arbitrarily long duration, as if it was consisted of photons whose energy matches the energy gap of the particle. This type of interaction is possible when the field is in a specially tailored state whose magnetic field's expectation value is a superoscillatory function.
Linear optics quantum logic gates are the best tool to generate multi-photon entanglement. Simplifying a recent approach [Phys. Rev. A 65, 062324; Phys. Rev. A 66, 024308] we were able to implement the conditional phase gate with only one second order interference at a polarization dependent beam splitter, thereby significantly increasing its stability. The improved quality of the gate is evaluated by analysing its entangling capability and by performing full process tomography. The achieved results ensure that this device is well suited for implementation in various multi photon quantum infor…
Recent work using spontaneous parametric down-conversion (SPDC) has made possible investigations of the Einstein-Podolsky-Rosen paradox in its original (position-momentum) form. We propose an experiment that uses SPDC photon pairs to measure through which slit a photon passes while simultaneously observing double-slit interference.
It was suggested in Ref. [Phys. Rev. Lett. 114, 170802] that optical networks with relatively inexpensive overhead---single photon Fock states, passive optical elements, and single photon detection---can show significant improvements over classical strategies for single-parameter estimation, when the number of modes in the network is small (n < 7). A similar case was made in Ref. [Phys. Rev. Lett. 111, 070403] for multi-parameter estimation, where measurement is instead made using photon-number resolving detectors. In this paper, we analytically compute the quantum Cramér-Rao bound to show the…
Fast, high efficiency, and low error single photon sources are required for implementation of a number of quantum information processing applications. The fastest triggered single photon sources to date have been demonstrated using epitaxially grown semiconductor quantum dots (QDs), which can be conveniently integrated with optical microcavities. Recent advances in QD technology, including demonstrations of high temperature and telecommunications wavelength single photon emission, have made QD single photon sources more practical. Here we discuss the applications of single photon sources and t…
We refute in this Reply the criticisms made by M. Abdel-Aty [Phys. Rev. A 70, 047801 (2004)]. We show that none of them are founded and we demonstrate very explicitly what is wrong in the arguments developed by this author.
As typically implemented, single photon sources cannot be made to produce single photons with high probability, while simultaneously suppressing the probability of yielding two or more photons. Because of this, single photon sources cannot really produce single photons on demand. We describe a multiplexed system that allows the probabilities of producing one and more photons to be adjusted independently, enabling a much better approximation of a source of single photons on demand.
Contrary to the claims made in Ref. [1], the recent Bell tests by Giustina et al. and Shalm et al. do not suffer from a "photon identification loophole". The model discussed in Ref. [1] is exploiting the well-known detection loophole, that is precisely what was closed in the recent experiments.
When a single emitter is excited by two phase-coherent pulses with a time delay, each of the pulses can lead to the emission of a photon pair, thus creating a ``time-bin entangled'' state. Double pair emission can be avoided by initially preparing the emitter in a metastable state. We show how photons from separate emissions can be made indistinguishable, permitting their use for multi-photon interference. Possible realizations are discussed. The method might also allow the direct creation of n-photon entangled states (n>2).
This comment refutes the claim made by A. Jadczyk and A.M. Schlichtinger in arXiv:2203.14555 that the photon position operator with commuting components proposed in 1999 does not have the properties required for a photon position operator.
A class of strictly localized states which can be made arbitrarily close to single photons is constructed, and expressions for central properties are provided. It is demonstrated that single photon states can be well approximated by these states down to localization scales on the order of a few pulse cycles. The results readily generalize to states close to $n$-photons. We also provide upper and lower bounds for the fidelity between a given single photon and any state strictly localized to a given volume. These results constitute the limit of photon localization, complementary to the weak-loca…
Single photon detectors are important for a wide range of applications each with their own specific requirements, which makes necessary the precise characterization of detectors. Here, we present a simple and accurate methodology of characterizing dark count rate, detection efficiency, and after-pulsing in single photon detectors purely based on their counting statistics. We demonstrate our new method on a custom-made, free-running single photon detector based on an InGaAs based avalanche photo diode (APD), though the methodology presented here is applicable for any type of single photon detec…
The quantum state of a single photon stands among the most fundamental and intriguing manifestations of quantum physics. At the same time single photons and pairs of single photons are important building blocks in the fields of linear optical based quantum computation and quantum repeater infrastructure. These fields possess enormous potential and much scientific and technological progress has been made in developing individual components, like quantum memories and photon sources using various physical implementations. However, further progress suffers from the lack of compatibility between th…
In the last two decades, considerable advances have been made in the investigation of nano-photonics in photonic crystals. Previous theoretical investigations of photon dynamics were carried out at zero temperature. Here, we investigate micro/nano cavity photonics in photonic crystals at finite temperature. Due to photonic-band-gap-induced non-Markovian dynamics, we discover that cavity photons in photonic crystals do not obey the standard Bose-Einstein statistical distribution. Within the photonic band gap and in the vicinity of the band edge, cavity photons combine nontrivial quantum dissipa…
We provide a theoretical framework to study the effect of dephasing on the quantum indistinguishability of single photons emitted from a coherently driven cavity QED $Λ$-system. We show that with a large excited-state detuning, the photon indistinguishability can be drastically improved provided that the fluctuation rate of the noise source affecting the excited state is fast compared with the photon emission rate. In some cases a spectral filter is required to realize this improvement, but the cost in efficiency can be made small.
We observe that a mesoscopic field made of several tens of microwave photons exhibits quantum features when interacting with a single Rydberg atom in a high-Q cavity. The field is split into two components whose phases differ by an angle inversely proportional to the square root of the average photon number. The field and the atomic dipole are phase-entangled. These manifestations of photon graininess vanish at the classical limit. This experiment opens the way to studies of large Schrodinger cat states at the quantum-classical boundary.
We answer the question whether linear-optical processing of the states produced by one or multiple imperfect single-photon sources can improve the single-photon fidelity. This processing can include arbitrary interferometers, coherent states, feedforward, and conditioning on results of detections. We show that without introducing multiphoton components, the single-photon fraction in any of the single-mode states resulting from such processing cannot be made to exceed the efficiency of the best available photon source. If multiphoton components are allowed, the single-photon fidelity cannot be …
The state obtained when a single photon impinges on a balanced beamsplitter is often known as single-photon entangled and its nonlocal properties have been the subject of intense debates in the quantum optics and foundations communities. It is however clear that a standard Bell test made only of passive optical elements cannot reveal the nonlocality of this state. We show that the nonlocality of single-photon entangled states can nevertheless be revealed in a quantum network made only of beamsplitters and photodetectors. In our protocol, three single-photon entangled states are distributed in …
Much of the richness in nature emerges because the same simple constituents can form an endless variety of ordered states. While many such states are fully characterized by their symmetries, interacting quantum systems can also exhibit topological order, which is instead characterized by intricate patterns of entanglement. A paradigmatic example of such topological order is the Laughlin state, which minimizes the interaction energy of charged particles in a magnetic field and underlies the fractional quantum Hall effect. Broad efforts have arisen to enhance our understanding of these orders by…
The recent discovery of room temperature intrinsic single-photon emitters in silicon nitride (SiN) provides the unique opportunity for seamless monolithic integration of quantum light sources with the well-established SiN photonic platform. In this work, we develop a novel approach to realize planar waveguides made of low-autofluorescing SiN with intrinsic quantum emitters and demonstrate the single-photon emission coupling into the waveguide mode. The observed emission coupling from these emitters is found to be in line with numerical simulations. The coupling of the single-photon emission to…
We consider photons strongly coupled to the excitonic excitations of a coupled quantum well, in the presence of an electric field. We show how under a field increase, the hybrid polariton made of photon coupled to hybrid carriers lying in the two wells, transforms into a dipolariton made of photon coupled to direct and indirect excitons. We also show how the cavity photon lifetime and the coherence time of the carrier wave vectors, that we analytically handle through non-hermitian Hamiltonians, affect these polaritonic states. While the hybrid polaritons display a spectral singularity, where t…
Stationary photon-atom entanglement is discussed by applying the method of flow equation to the Jaynes-Cummings model. A nonlocal continuous unitary transformation is explicitly constructed and the associated positive operator-valued measures for the photons and atom are obtained. Then, flow of the entanglement entropy is analyzed. A comment is also made on implementing the unitary operation in the method of flow equation. This method may offer a new strategy for quantum-state engineering.
We propose and analyze a probabilistic but heralded scheme to generate pure, entangled, non-Gaussian states of collective spin in large atomic ensembles by means of single-photon detection. One photon announces the preparation of a Dicke state, while two or more photons announce Schrödinger cat states. The method produces pure states even for finite photon detection efficiency and weak atom-photon coupling. The entanglement generation can be made quasi-deterministic by means of repeated trial and feedback, enabling metrology beyond the standard quantum limit.
Achieving the regime of single-photon nonlinearities in photonic devices just exploiting the intrinsic high-order susceptibilities of conventional materials would open the door to practical semiconductor-based quantum photonic technologies. Here we show that this regime can be achieved in a triply resonant integrated photonic device made of two coupled ring resonators, without necessarily requiring low volume confinement, in a material platform displaying an intrinsic third-order nonlinearity. By strongly driving one of the three resonances of the system, a weak coherent probe at one of the ot…
We propose the use of nanostructured photonic nanocavities made of second-order nonlinear materials as prospective passive devices to generate strongly sub-Poissonian light via single-photon blockade of an input coherent field. The simplest scheme is based on the requirement that the nanocavity be doubly resonant, i.e. possess cavity modes with good spatial overlap at both the fundamental and second-harmonic frequencies. We discuss feasibility of this scheme with state-of-the art nanofabrication technology, and the possibility to use it as a passive single-photon source on-demand.
The fast development of superconducting nanowire single photon detector (SNSPD) in the past decade has enabled many advances in quantum information technology. The best system detection efficiency (SDE) record at 1550 nm wavelength was 93% obtained from SNSPD made of amorphous WSi which usually operated at sub-kelvin temperatures. We first demonstrate SNSPD made of polycrystalline NbN with SDE of 90.2% for 1550 nm wavelength at 2.1K, accessible with a compact cryocooler. The SDE saturated to 92.1% when the temperature was lowered to 1.8K. The results lighten the practical and high performance …
Generation of a single photon or a pair of photons from a single emitter is important for quantum information applications. Using the generating function formalism we investigate the theory of a few photons on demand for the square laser pulse and the rapid adiabatic following method. Exact theory and numerical solutions are used to design control fields for a two level emitter, which yield an optimal single or two photon source, under the constrains of finite laser field strength and finite interaction time. Comparison to experiments of Brunel et al, shows that the experiments were made close…
We solve for the exact atom-field eigenstates of a single atom in a three dimensional spherical cavity, by mapping the problem onto the anisotropic Kondo model. The spectrum has a rich bound state structure in comparison with models where the rotating wave approximation is made. It is shown how to obtain the Jaynes-Cummings model states in the limit of weak coupling. Non-perturbative Lamb shifts and decay rates are computed. The massive Kondo model is introduced to model light localization in the form of photon-atom bound states in photonic crystals.
