Single-photon Interference Experiment Research Articles

Validation of classical modeling of single-photon pulse propagation

"It is well-known to those who know it" that single-photon interference experiments can be modeled classically [S. Barnett, arXiv:2207.14632 (2022)]. When a single-photon light pulse was split by a biprism good agreement with a classical fit was obtained and the photon was counted only once, consistent with a probabilistic interpr.etation [V. Jacques et al, Eur. Phys. J. D 35, 561 (2002)]. A justification for this "well know result of Quantum Optics" is implicit in [M. Hawton, Phys. Rev A 104, 052211 (2021)] where a real covariant field describing a single photon is first quantized. Here the theoretical basis of this result is reviewed and the theory is extended to multiphoton states and QED Fock space. The crucial role of the CPT theorem in coupling to charged matter and resolution of the photon localization problem is discussed.

On single-photon and classical interference

It has often been remarked that single-photon interference experiments, however complicated, seem to behave very much in the same way as those performed in the classical regime, using the field generated by a laser. This observation has the status of being ‘well-known to those who know it’, but perhaps mysterious to others. We discuss the reasons underlying the similarity and also some of the limitations of this simple idea.

Photon heterodyning.

Single-photon interference experiments are attempted in the time domain using true single-photon streams. Self-heterodyning beats are clearly observed by letting the field associated with a single photon interfere with itself on a field-quadratic detector, which is a time analogue of Young's two-slit interference experiment. The temporal first-order coherence of single-photon fields, i.e., transient interference fringes, develops as cumulative detection events are mapped point-by-point onto a virtual capture frame by properly correlating the time-series data. The ability to single out photon counts at a designated timing paves the way for digital heterodyning with faint light for such use as phase measurement and quantum information processing.

Complementarity in biphoton generation with stimulated or induced coherence

Coherence can be induced or stimulated in parametric down-conversion using two or three crystals when, for example, the idler modes of the crystals are aligned. Previous experiments with induced coherence [Phys. Rev. Lett. 114, 053601 (2015)] focused on which-path information and the role of vacuum fields in realizing complementarity via reduced visibility in single-photon interference. Here we describe experiments comparing induced and stimulated coherence. Different single-photon interference experiments were performed by blocking one of the pump beams in a three-crystal setup. Each counted photon is emitted from one of two crystals and which-way information may or not be available, depending on the setup. Distinctly different results are obtained in the induced and stimulated cases, especially when a variable transmission filter is inserted between the crystals. A simplified theoretical model accounts for all the experimental results and is also used to address the question of whether the phases of the signal and idler fields in parametric down-conversion are correlated.

Sagnac 형태로 변형된 Mach-Zehnder 간섭계를 이용한 단일광자 간섭실험

Sagnac 형태로 변형된 Mach-Zehnder 간섭계(SMZI)는 모든 광경로가 동일한 광부품을 서로 공유하기 때문에 위상 흔들림을 최소화할 수 있는 안정된 간섭계이다. 본 연구에서는 단일광자 수준까지 감쇄시킨 레이저 광과 제 2형의 매개하향변환에서 발생한 편광 상관관계가 있는 광자로부터 준비된 단일광자를 이용한 간섭실험에서 매우 안정된 간섭무늬를 관측하였다. SMZI의 위상은 약 <TEX>${\pm}0.18$</TEX> rad으로 안정적인 반면에 보통의 MZI는 <TEX>${\pm}1.02$</TEX> rad의 위상 요동을 나타내었다. A Sagnac-type Mach-Zehnder interferometer(SMZI) is a very stable instrument with respect to phase drift because all optical paths can share common optical components. We have observed very stable interference fringes in single photon interference experiments with an extremely attenuated laser beam, and with heralded single photons prepared from polarization correlated photon pairs in type-II spontaneous parametric down-conversion. The phase stability is measured to be about <TEX>${\pm}0.18$</TEX> rad for the SMZI, in contrast, conventional MZI showed the phase fluctuation of around <TEX>${\pm}1.02$</TEX> rad.

Wave-particle duality and polarization properties of light in single-photon interference experiments

It is shown that the degree of polarization of light, generated by superposition in a single-photon interference experiment, may depend on the indistinguishability of the photon-paths.

Corpuscular Model of Two-Beam Interference and Double-Slit Experiments with Single Photons

We introduce an event-based corpuscular simulation model that reproduces the wave mechanical results of single-photon double-slit and two-beam interference experiments and (of a one-to-one copy of an experimental realization) of a single-photon interference experiment with a Fresnel biprism. The simulation comprises models that capture the essential features of the apparatuses used in the experiment, including the single-photon detectors recording individual detector clicks. We demonstrate that incorporating in the detector model, simple and minimalistic processes mimicking the memory and threshold behavior of single-photon detectors is sufficient to produce multipath interference patterns. These multipath interference patterns are built up by individual particles taking one single path to the detector where they arrive one-by-one. The particles in our model are not corpuscular in the standard, classical physics sense in that they are information carriers that exchange information with the apparatuses of the experimental set-up. The interference pattern is the final, collective outcome of the information exchanges of many particles with these apparatuses. The interference patterns are produced without making reference to the solution of a wave equation and without introducing signalling or non-local interactions between the particles or between different detection points on the detector screen.

Stabilization of a long-armed fiber-optic single-photon interferometer

We report on single-photon interference experiments in a Michelson-type interferometer built with two 6-km-long fiber spools, as well as on the active stabilization of the interferometer. A weak coherent light signal was (de-) multiplexed with a strong reference light using wavelength-division multiplexing technique, and real-time feedback control technique was applied for the reference light to actively stabilize the phase fluctuation in the long-armed fiber interferometer. The stabilized interferometer showed phase stability of 0.06 rad, which corresponds to an optical path length fluctuation of 15 nm between the 6-km-long interfering arms. The raw visibility obtained without subtracting noise counts in the single-photon interference experiment was more than 98% for stabilized conditions.

Single-Photon Interference Experiment Over 80 km With a Pulse-Driven Heralded Single-Photon Source

We have conducted a single-photon interference experiment over an 80-km optical fiber using a pulse-driven heralded single-photon source (HSPS). To the best of our knowledge, this is, thus far, the longest distance over which a single-photon interference experiment has been conducted using HSPSs (continuous-wave-pumped or pulse-driven). The effect of the 80-km transmission on the dispersion and fluctuation of polarization are more severe than those in our previous 40-km quantum key distribution (QKD) experiment. We have overcome the difficulties by some fine tunings and low-jitter controlling. By conducting ten consecutive transmission experiments over a total time of 30 min, an average quantum bit-error rate (QBER) of 7.9 plusmn 1.2% has been obtained. This QBER is lower than the threshold QBER of 10.55% which is considered as a limit for unconditional security for the QKD under negligible multiphoton emission.

Color Centers in Diamond as Practical Single-Photon Source to Illustrate Quantum Complementarity

ABSTRACTA recent experiment performed by S. S. Afshar [reviewed in M. Chown, New Scientist183, 30 (2004)] has been interpreted as a possible violation of the complementarity principle of quantum mechanics. Starting from a single-photon wavefront-splitting interference experiment, we propose a new scheme for Afshar's experiment, and we show that Afshar's interpretation is incorrect. Furthermore, this design is well suited to illustrate the complementarity inequality in the interesting intermediate regimes with partial fringe visibility and partial which-path information.

Experimental demonstration of complementarity with single photons

We demonstrate the principle of complementarity in quantum mechanics in a single-photon interference experiment. Single photons are provided by isolated, optically pumped nitrogen-vacancy centers in diamond, which can be easily addressed by confocal microscopy. In order to observe the particle-like behavior of photons, we perform an elementary Welcher-Weg measurement, detecting photons behind a beam splitter. In contrast, if we dispense with this Welcher-Weg information, we observe interference fringes with a visibility of about 96%, revealing the wave nature of the photon.

Single-photon interference experiment over 100 km for quantum cryptography system using balanced gated-mode photon detector

The authors demonstrate single-photon interference over 100 km using a balanced gated-mode photon detector and a plug and play system for quantum key distribution. The visibility with 0.1 photon/pulse was more than 80% after 100 km transmission. This corresponds to the fidelity of a quantum cryptography system of more than 90% and a QBER of less than 10%, satisfying the security criteria.

Stochastic and deterministic absorption in single-photon interference experiments

We performed single-photon interference experiments with neutral density filters and slow beam choppers to confirm the difference between stochastic and deterministic absorption and obtained results that agreed with the case of neutron-interference experiments and quantum theory.

Complementarity and Fundamental Limit in Precision Phase Measurement.

By analyzing a single-photon interference experiment together with a quantum nondemolition measurement scheme for the which-path information, we prove that given the total mean number $〈n〉$ of available photons, the fundamental limit in precision measurement of a phase shift is the Heisenberg limit, i.e., $1/〈n〉$. The analysis is based on the complementarity principle and is independent of the scheme for the measurement of the phase shift. We also show that to achieve the Heisenberg limit states with photon number fluctuations of the order of or larger than the mean photon number have to be exploited.

Single-photon interference experiment using a mechanical frequency shifter

A variation of the interference experiment on the single photon has been performed. By means of a mechanical effect, we change the frequency of the photon only on one arm of a Mach-Zender interferometer. We observe the beat signals even when the intensity is so small that only one photon at a time passes through the interferometer. Our experiment gives a further proof of the classical behaviour of the electromagnetic radiation at arbitrarily small intensity, in agreement with the probabilistic interpretation of quantum mechanics.

Statistical explanation in physics: The Copenhagen interpretation

The statistical aspects of quantum explanation are intrinsic to quantum physics; individual quantum events are created in the interactions associated with observation and are not describable by predictive theory. The superposition principle shows the essential difference between quantum and non-quantum physics, and the principle is exemplified in the classic single-photon two-slit interference experiment. Recently Mandel and Pfleegor have done an experiment somewhat similar to the optical single-photon experiment but with two independently operated lasers; interference is obtained even with beam intensity so small that only one photon is in the apparatus at a time. The result can be understood in terms of the superposition of states; or, in terms of the Uncertainty Principle, which is found to forbid the determination of which of the two lasers is the source of a given photon (if conditions for interference are to obtain). The Mandel-Pfleegor experiment gives a physical argument against the continuous localization of a photon that is assumed in the ‘hidden variable’ theories and therefore gives further support for the generally accepted view that an observed entity (observed state) is created in the observation event. This aspect of quantum physics implies a subjectivism on the level of individual quantum-level occurrences, since there is in quantum theory no basis for asserting the existence of the event independently of observation of it. Extension of this subjectivism to large scale, non-quantum phenomena falls within the principles of quantum theory; counter considerations that argue against such an extension are noted.

Direct recovery of ammonia as sulphate, without distillation: W. Strommenger. ( Stahl und Eisen, xli 1694.)

Quantum mechanics is the theory used to describe microscopic systems such as atoms, molecules, and elementary particles. It grew early in this century from a synthesis of Planck's introduction of the elementary quantum of action to understand the observed spectrum for blackbody radiation, Einstein's use of the quantum of action to explain the photoelectric effect, and Bohr's combination of the planetary model of the atom and the quantum of action to create a description of the hydrogen atom with a distinct set of stationary energy states. The present form of the nonrelativistic theory was developed independently by Schrodinger through the use of a wave equation that was motivated by work by de Broglie and by Heisenberg through an algebraic analysis based on a calculus of observables and motivated by dispersion theory relationships. This chapter first reviews the present conceptual basis for quantum mechanics and then describes the experiments that have been carried out to test these concepts. The relevant experiments are precision measurements of the predicted eigenvalue spectrum, single-photon interference experiments, successive measurements on eigenstates, measurements of photon-photon and spin correlations as a test of Bell's inequality, and the observation of the sign change for the rotation of the neutron through 2π rad. Earlier reviews that summarize some of the information presented here are given by Paty, Freedman and Holt, and Freedman.