Review the time-resolved scattering of a single photon by a single atom

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1 H. Javadi 1, F. Forouzbakhsh 2 1 Faculty of Science, Islamic Azad University, South Tehran Branch, Tehran, Iran Javadi_hossein@hotmail.com 2 Department of Energy Technology, Aalborg University, Esbjerg, Denmark faf@et.aau.dk Dec. 8, 2016 Introduction Scattering of light by matter has been studied extensively in the past. Yet, the most fundamental process, the scattering of a single photon by a single atom, is largely unexplored. One prominent prediction of quantum optics is the deterministic absorption of a travelling photon by a single atom, provided the photon waveform matches spatially and temporally the time-reversed version of a spontaneously emitted photon. [1 and figures] Here we experimentally address this prediction and investigate the influence of the photon s temporal profile on the scattering dynamics using a single trapped atom and heralded single photons. We don't often think of photons as being spread out in time and space and thus having a shape, but the ones in this experiment were some four meters long. Christian Kurtsiefer, Principal Investigator at CQT, and his team have learned to shape these photons with extreme precision. [2] 1

2 According to the quantum mechanics that photon is an unstructured particle. How the concept of unstructured photon is able to describe the different shapes and four meter long of photon? In addition to four meters long and shapes of photons, how two opposites charged particles such as electron and positron absorb and emit neutral and unstructured photons? There are many articles that show, photon has upper limit mass and electric charge, which are consistent with experimental observations [3 and 4]. However, in CPH theory photons are combination of positive and negative virtual photons. Photon is a very weak electric dipole that is consistent with the experience and these articles are asserted. In addition, this property of photon (very weak electric dipole) can describe the absorption and emission energy by charged particles. Structure of photon To understand the structure of photon, there are at least two ways 1. Generalization of the Dirac s equation and Sea 2. The behavior of photons in the gravitational field Fortunately, both ways reach to the same results. 1- Generalization of the Dirac s Equation and Sea We have reconsidered Dirac equation and Sea several times. In the last edition by reconsidering the Dirac Sea and his equation, the structure of photon is investigated and it is made an attempt to answer these following questions: 1- What is the relation between photon and its electromagnetic fields? 2- Does force have physical existence or it is just a mathematical tool to describe physical interactions? 3- What is the mechanism of converting potential energy to kinetic energy and vice versa? 4-What is the relation between gravity and electromagnetics? 5-What is the relation between Weyl fermions and Dirac fermions? To access the latest editing, see the following article: H. Javadi, et. al,"generalization of the Dirac s Equation and Sea", General Science Journal,

3 2- Photon-Graviton Interaction and CPH Theory In recent decades, the structure of photon is discussed. In this article, description the structure of photon is based on the behavior of photons in a gravitational field, leading to a new a definition of the graviton too. In effect, gravitons behave as if they have charge and magnetic effects. These are referred to as negative color charge, positive color charge and magnetic color. From this, it can be shown that a photon is made of color charges and magnetic color. To access the latest editing, see the following article: H. Javadi, et. al, "Photon-Graviton Interaction and CPH Theory", General Science Journal, Graviton_Interaction_and_CPH_Theory?ev=prf_pub To learn more about the CPH Theory see the following articles: H. Javadi, et. al,"adaptive Review of Three Fundamental Questions in Physics", General Science Journal, _Questions_in_Physics?ev=prf_pub H. Javadi, et. al, " What is CPH Theory?", General Science Journal, CONCLUSION Classical mechanics and both special and general relativity describe outward of phenomena regardless the properties of sub quantum scales. At the beginning of the 20th century, Newton s second law was corrected considering the limit speed c and the relativistic mass. At that time there has not been a clear understanding of the subatomic particles and basically there was little research in high energy physics. Also, in quantum mechanics, the concept of a point particle is complicated by the Heisenberg uncertainty principle, because even an elementary particle, with no internal structure, occupies a nonzero volume. 3

4 It should be noted that the interaction between large objects (e.g. collision of two bodies) under the action of the sub quantum layer done. Attention to photon structure and using new definitions for graviton, charged and exchange particles will change our perspective on modern physics. It also provides us with a new tool to be able to overcome physics problems in a better way. In addition, the root of the quantum gravity problem is that physicists want to solve the quantum gravity problem regardless to the classical mechanics. Thus CPH Theory, from a new approach, turns out to merge the fundamental principles of quantum physics, relativity and classical mechanics. References [1] Victor Leong, et. al., "Time-resolved scattering of a single photon by a single atom", Nature Communications (2016). DOI: /ncomms Preprint available at: [2] Mapping the interaction of a single atom with a single photon may inform design of quantum devices, Phys.org, December 2, 2016, available at: [3] Heeck, J. (2013). How stable is the photon? Physical review letters, 111(2), Liang-Cheng Tu, Jun Luo and George T Gillies, "The mass of the photon" Rep. Prog. Phys. 68 (2005) , doi: / /68/1/r02 Antonio Accioly, Jos e Helay el-neto, and Eslley Scatena, "Upper bounds on the photon mass", Phys.Rev.D82:065026,2010, DOI: /PhysRevD [4] Giuseppe Cocconi, "Upper limit for the electric charge of the photons from the millisecond pulsar observations" Physics Letters B Volume 206, Issue 4, 2 June 1988, Pages V. V. Kobychev and S. B. Popov, "Constraints on the Photon Charge from Observations of Extragalactic Sources" Astronomy Letters, Vol. 31, No. 3, 2005, pp C Sivaram and Kenath Arun "Some Additional Bounds on the Photon Charge" L.B. Okun, "PHOTON: HISTORY, MASS, CHARGE", ACTA PHYSICA POLONICA B Vol. 37 (2006) 4

5 Figures: Fig 1: Scientists at the Centre for Quantum Technologies at the National University of Singapore have shown that a photon's shape affects how it is absorbed by a single atom. This artist's illustration is not to scale: in the experiment the photons are some 4 meters long, while the atom is less than a nanometer wide. Credit: Timothy Yeo / Centre for Quantum Technologies, National University of Singapore. [2] Figure 2: Single photon scattering by a two-level atom in free space. The time evolution of the atomic excited state population is inferred by measuring photons in the forward or backward direction. D f and D b: forward and backward detectors, g and e : ground and excited levels of the atom. [1] 5

6 Figure 3: Experimental setup and level schemes. (a) (Top left) Four-wave mixing part, providing heralded single photons: pump 1 (795 nm) and pump 2 (762 nm) are overlapped in a copropagating geometry inside the cold cloud of 87 Rb atoms in a magneto-optical trap (MOT), generating pairs of herald (776 nm) and probe (780 nm) photons. The detection of a photon at D h heralds a probe photon. (Top right) Tuning the resonance of a bandwidth-matched cavity with respect to the heralding photon frequency controls the temporal envelope. (Bottom) Single atom part: A 87 Rb atom is trapped at the focus of a confocal aspheric lens pair (AL; numerical aperture 0.55) with a far-off-resonant optical dipole trap (980 nm). The probe photons are guided to the single atom part by a single mode fibre and focused onto the atom by the first AL. Avalanche photodetectors D f and D b detect photons collected in forward and backward directions. An acousto-optic modulator (AOM) shifts the probe photon frequency to compensate for the shift of the atomic resonance frequency caused by the bias magnetic field and the dipole trap. λ/2, λ/4, half- and quarter-wave plates; D h, D f, D b, avalanche photodetectors (APDs); DM, dichroic mirror; F, interference filter; PDH lock, Pound Drever Hall frequency lock electronics; P, polarizer; (P)BS, (polarizing) beam splitter. (b) Relevant level scheme of the four-wave mixing process in a cloud of 87 Rb atoms. (c) Relevant level scheme of the single 87 Rb atom in the dipole trap. The probe photons are resonant with the closed transition g =5 S 1/2, F=2, m F= 2 to e =5 P 3/2, F=3, m F= 3. [1] 6