Variational Quantum Computation of Excited States

Total Page:16

File Type:pdf, Size:1020Kb

Variational Quantum Computation of Excited States Variational Quantum Computation of Excited States Oscar Higgott1,2, Daochen Wang1,3, and Stephen Brierley1 1 Riverlane, 3 Charles Babbage Road, Cambridge CB3 0GT 2 Department of Physics and Astronomy, University College London, London, WC1E 6BT 3Joint Center for Quantum Information and Computer Science, University of Maryland, College Park, MD 20742 July 1, 2019 The calculation of excited state energies of materials, or to understand some chemical reactions, electronic structure Hamiltonians has many im- such as those that involve photodissociation. However, portant applications, such as the calculation of classical methods such as density functional theory are optical spectra and reaction rates. While low- often unable to determine excited states, even for ma- depth quantum algorithms, such as the varia- terials where ground state energy calculations are pos- tional quantum eigenvalue solver (VQE), have sible. been used to determine ground state ener- Quantum computers have the potential to solve these gies, methods for calculating excited states cur- and other problems significantly faster than any known rently involve the implementation of high-depth methods using classical computers [1, 11, 19, 36]. How- controlled-unitaries or a large number of addi- ever many quantum algorithms will require quantum tional samples. Here we show how overlap esti- error correction, limiting their usefulness in the near mation can be used to deflate eigenstates once future [31]. Here we study hybrid quantum-classical al- they are found, enabling the calculation of ex- gorithms, which dramatically reduce the required gate cited state energies and their degeneracies. We depth to run and somewhat mitigate errors, by closely propose an implementation that requires the integrating classical and quantum subroutines [2,9, 14, same number of qubits as VQE and at most twice 15, 21, 23, 26, 40]. the circuit depth. Our method is robust to con- The variational quantum eigensolver (VQE), intro- trol errors, is compatible with error-mitigation duced in Ref. [30], is the first algorithm designed to strategies and can be implemented on near-term find the lowest eigenvalue of a Hamiltonian on a near- quantum computers. term, non-fault-tolerant quantum computer. VQE is based on the variational principle and utilises the fact 1 Introduction that quantum computers can store quantum states us- ing exponentially fewer resources than required classi- Eigenvalue problems are ubiquitous in almost all fields cally. VQE uses parameterised quantum circuits to pre- of science and engineering. Google's PageRank al- pare trial wavefunctions and compute their energy, and gorithm alone has had a significant impact on mod- a classical computer to find the parameters minimising ern society, and at its core solves an eigenvalue prob- this energy. The low circuit depth of VQE has led to the lem associated with a stochastic matrix describing the hope that it may enable near-term quantum-enhanced World Wide Web [28]. Another important example is computation. Principal Component Analysis (PCA) [13, 29], which Since its introduction, modifications have been sug- arXiv:1805.08138v5 [quant-ph] 28 Jun 2019 has widespread applications in bioinformatics, neuro- gested to enable VQE to find excited state ener- science, image processing, and quantitative finance. gies: e.g. a folded spectrum method [30] which re- The time-independent Schr¨odinger equation provides quires finding the expectation of the squared Hamil- yet another example of a fundamental eigenvalue prob- tonian with quadratically more terms, or symmetry- lem. Its numerical solution enables properties of atoms, based methods which are non-systematic [23]. Such molecules and materials to be predicted, with far- suggestions have been more recently superseded by reaching applications in materials design, drug discov- two proposals: a method that minimises the von Neu- ery and fundamental science [38]. Characterisation of mann entropy [35] and the quantum subspace expansion excited state energies of molecules is required to predict method [5, 24]. However, the von Neumann entropy charge and energy transfer processes in photovoltaic method (\WAVES") requires a large number of high- depth controlled-unitaries, and the quantum subspace Oscar Higgott: [email protected] expansion method requires a large number of additional Accepted in Quantum 2019-06-14, click title to verify 1 VARIATIONAL QUANTUM DEFLATION ALGORITHM (VQD) samples compared to VQE and introduces a new ap- QUANTUM CIRCUITS CLASSICAL CIRCUITS proximation. Expectation estimation i ) Our algorithm extends VQE to systematically find k of (λk) P1 (λk) λ h | | i ( excited states at almost no extra cost. We achieve this | i H 2 0 | | | Expectation estimation ) i ) k k of (λk) P2 (λk) λ by adding \overlap" terms onto the optimisation func- ( h | | i λ ( | ) ... i tion in order to exploit the fact that Hermitian ma- ⌘h λ ) to minimise ( k k Expectation estimation λ h λ ( | Classical adder calculates trices admit a complete set of orthogonal eigenvectors. i of (λk) Pn (λk) E h | | i β 1 from fiducial state − =0 k i Exploiting further the fact that VQE retains the clas- i ) P k λ ( Overlap estimation sical parameters of ansatz states that enable their re- 2 | | 2 )+ i of (λ ) (λ ) k 0 k ) λ |h | i| k ( λ ( preparation, low-depth quantum circuits can then be E | Overlap estimation ) i 2 = λ ) prepares readily used to calculate these overlap terms. of (λ1) (λk) ( k |h | i| λ h obj ( | Classical optimiser updates F i R β ... 1 − =0 k Overlap estimation i 2 P of (λk 1) (λk) Classical adder calculates 2 Variational quantum deflation algo- |h − | i| rithm <latexit sha1_base64="yR/JbkSxD+62BkpgO63Wfjq2Z7A=">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</latexit>sha1_base64="YP815qoE3qu0PCW3l0Rz70PuABw=">AAAT4XiczVjdbxNHEDe0BZp+QMhjX5ZiJEfY7t2FFFB1iDRAiRS+QhKQbGOt79b21ne7x+4eiXH8B/St6mvVv4v2D+ljpc7ene07f3AhIlUtWVrPzsdvZnZmdt0KPCqVYfx15uwnn3527vyFz5e++PKrry9eWr68L3koHLLncI+Lly0siUcZ2VNUeeRlIAj2Wx550ept6v0Xb4iQlLNd1Q9Iw8cdRtvUwQpIzeXloK5o761UfY8MpMJCScWDIbJRTRBHYdbxSBkJHjKXuMjhgoGyMvIpo37oowPqqq695vgTUpfQTlfZJtAUOVTIIUwRQdwycgU+sFsednpl1KaeZwP1yprRWEpBoDyyrQQOyFsagt7xEnmkrVCEyL5ppDeEtpjsmKZxXHgoD1/LC8k0wEBwh0g5HaGPZJEL0Ddj0yUO1RmMjLoU+5y5H81kRxDC/g9eJjatUzL6Pj/XTsnmvAP03ycTC8EP4rLqUmCt3CnfsaUi2FPdESNRA4czhaGNiO+qkZw90Oqh+CdhcbHsaruUARuSJLAt4g+HS/UW6VA20JoC6qhQkGGNcZcgFzoYZg6xLccHUxGtBA0qWEW1Ub51e1FYEfv2TOWaRlULokFxp1T3oKu5uNlbLSKtAQsiUbHeA+T1QNLU/rCI2oL7EBE3dCj2kNTqE15jWBz+MEJCDgNzgqSMcIu/IUk7sRFvR4aSqMeIbugs9GWXtpVdsarr+udh/NOMkN4/DHS8dHdFRCrqx0vQVay3BJ7B+rRpzvchg9JKo2wRjx+ARlvDX4jO0OBOBMg6BiC2CJA1DehEEFgOBKxQqRgH5kp1/UqMqAiYxkcJzNY9lys5gS0P0tley+Jmc3A/gcnp4WAGczSIjjT0GZTG6tE06np8no5eWcUMFms+Fo0yN6knQGYeH1lvIbJ52T0BlkGvYg6PhyfOdBSuKNMRvLxMQz6x6xKR7TKR8nHZpJpO2qXqWqqkK2b15vpMxYPBTQ9LCZcoD0V2EKyc0AN90JLup1yqk9chfYPmnvKHeWUGrr7Hi/icnJoXdRn6zQG1jeGrKFvgA1G4SVGSVzQ3sfR9SUUp38LABTsfMgUyDt6u3ko7BA5qh/RZGaW+Cldk1UVHlaiHx79W0y7zAI4rleB2jEX7PEJdRIrHIIABFR80B7z189BOZ/b6KQQoio8euqgWzexGPCsnrsTzqlJJJlc+tzXmto7BzcbcLI877qWaO1rlc1tj7lwkcQdKuHuz3Nr3KsFSjeHGGWdcTMIUM8yTtfJkrcWyLE+WLZDVUUrJjkp7IjthmCdr5ckuwqwjmCfbW+xvqpRiBXGtZFxO88yzn6tjigd0OJwLlzJ9ayu1sdAFtZpMguioRKKr10tQ+DfKle+r6zARZsWiuhrJJUZjE9dLWcEs5gxrpTJf2ABJ2BubidcR0khkFmcikdmKrOuOWBvfvvVNXtnJJTmuc8D0OsRMhT50sMxkTMhJLA+IznMtdYstZ2/hBjySXaQn5rO9jce7e4/Q5tbO5t7W7vPhIhyTUTrq2YDGGXXRaTzjjQ9HtLm98fz51ubGdj6mJDajGTI5IqmsjyOmD6HCjpyGGhE/HOb+xs7Wxu7Wk8cAdBTEe/cfbEc0tLH905Odrd2Hj1Bp/9m9VW2QMDfzMGpeumpUjeiDZhdmsrh699rff777Y6nztLl85mXd5U7ow7Mvim/NNALVgGedoo5H4PUVwksM3oC4Q2qwZNgnsjGI/hsaomtAcVGbC/gyeDtqalpigH0p+34LO
Recommended publications
  • Bouncing Oil Droplets, De Broglie's Quantum Thermostat And
    Preprints (www.preprints.org) | NOT PEER-REVIEWED | Posted: 28 August 2018 doi:10.20944/preprints201808.0475.v1 Peer-reviewed version available at Entropy 2018, 20, 780; doi:10.3390/e20100780 Article Bouncing oil droplets, de Broglie’s quantum thermostat and convergence to equilibrium Mohamed Hatifi 1, Ralph Willox 2, Samuel Colin 3 and Thomas Durt 4 1 Aix Marseille Université, CNRS, Centrale Marseille, Institut Fresnel UMR 7249,13013 Marseille, France; hatifi[email protected] 2 Graduate School of Mathematical Sciences, the University of Tokyo, 3-8-1 Komaba, Meguro-ku, 153-8914 Tokyo, Japan; [email protected] 3 Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud 150,22290-180, Rio de Janeiro – RJ, Brasil; [email protected] 4 Aix Marseille Université, CNRS, Centrale Marseille, Institut Fresnel UMR 7249,13013 Marseille, France; [email protected] Abstract: Recently, the properties of bouncing oil droplets, also known as ‘walkers’, have attracted much attention because they are thought to offer a gateway to a better understanding of quantum behaviour. They indeed constitute a macroscopic realization of wave-particle duality, in the sense that their trajectories are guided by a self-generated surrounding wave. The aim of this paper is to try to describe walker phenomenology in terms of de Broglie-Bohm dynamics and of a stochastic version thereof. In particular, we first study how a stochastic modification of the de Broglie pilot-wave theory, à la Nelson, affects the process of relaxation to quantum equilibrium, and we prove an H-theorem for the relaxation to quantum equilibrium under Nelson-type dynamics.
    [Show full text]
  • 5.1 Two-Particle Systems
    5.1 Two-Particle Systems We encountered a two-particle system in dealing with the addition of angular momentum. Let's treat such systems in a more formal way. The w.f. for a two-particle system must depend on the spatial coordinates of both particles as @Ψ well as t: Ψ(r1; r2; t), satisfying i~ @t = HΨ, ~2 2 ~2 2 where H = + V (r1; r2; t), −2m1r1 − 2m2r2 and d3r d3r Ψ(r ; r ; t) 2 = 1. 1 2 j 1 2 j R Iff V is independent of time, then we can separate the time and spatial variables, obtaining Ψ(r1; r2; t) = (r1; r2) exp( iEt=~), − where E is the total energy of the system. Let us now make a very fundamental assumption: that each particle occupies a one-particle e.s. [Note that this is often a poor approximation for the true many-body w.f.] The joint e.f. can then be written as the product of two one-particle e.f.'s: (r1; r2) = a(r1) b(r2). Suppose furthermore that the two particles are indistinguishable. Then, the above w.f. is not really adequate since you can't actually tell whether it's particle 1 in state a or particle 2. This indeterminacy is correctly reflected if we replace the above w.f. by (r ; r ) = a(r ) (r ) (r ) a(r ). 1 2 1 b 2 b 1 2 The `plus-or-minus' sign reflects that there are two distinct ways to accomplish this. Thus we are naturally led to consider two kinds of identical particles, which we have come to call `bosons' (+) and `fermions' ( ).
    [Show full text]
  • 8 the Variational Principle
    8 The Variational Principle 8.1 Approximate solution of the Schroedinger equation If we can’t find an analytic solution to the Schroedinger equation, a trick known as the varia- tional principle allows us to estimate the energy of the ground state of a system. We choose an unnormalized trial function Φ(an) which depends on some variational parameters, an and minimise hΦ|Hˆ |Φi E[a ] = n hΦ|Φi with respect to those parameters. This gives an approximation to the wavefunction whose accuracy depends on the number of parameters and the clever choice of Φ(an). For more rigorous treatments, a set of basis functions with expansion coefficients an may be used. The proof is as follows, if we expand the normalised wavefunction 1/2 |φ(an)i = Φ(an)/hΦ(an)|Φ(an)i in terms of the true (unknown) eigenbasis |ii of the Hamiltonian, then its energy is X X X ˆ 2 2 E[an] = hφ|iihi|H|jihj|φi = |hφ|ii| Ei = E0 + |hφ|ii| (Ei − E0) ≥ E0 ij i i ˆ where the true (unknown) ground state of the system is defined by H|i0i = E0|i0i. The inequality 2 arises because both |hφ|ii| and (Ei − E0) must be positive. Thus the lower we can make the energy E[ai], the closer it will be to the actual ground state energy, and the closer |φi will be to |i0i. If the trial wavefunction consists of a complete basis set of orthonormal functions |χ i, each P i multiplied by ai: |φi = i ai|χii then the solution is exact and we just have the usual trick of expanding a wavefunction in a basis set.
    [Show full text]
  • 1 the Principle of Wave–Particle Duality: an Overview
    3 1 The Principle of Wave–Particle Duality: An Overview 1.1 Introduction In the year 1900, physics entered a period of deep crisis as a number of peculiar phenomena, for which no classical explanation was possible, began to appear one after the other, starting with the famous problem of blackbody radiation. By 1923, when the “dust had settled,” it became apparent that these peculiarities had a common explanation. They revealed a novel fundamental principle of nature that wascompletelyatoddswiththeframeworkofclassicalphysics:thecelebrated principle of wave–particle duality, which can be phrased as follows. The principle of wave–particle duality: All physical entities have a dual character; they are waves and particles at the same time. Everything we used to regard as being exclusively a wave has, at the same time, a corpuscular character, while everything we thought of as strictly a particle behaves also as a wave. The relations between these two classically irreconcilable points of view—particle versus wave—are , h, E = hf p = (1.1) or, equivalently, E h f = ,= . (1.2) h p In expressions (1.1) we start off with what we traditionally considered to be solely a wave—an electromagnetic (EM) wave, for example—and we associate its wave characteristics f and (frequency and wavelength) with the corpuscular charac- teristics E and p (energy and momentum) of the corresponding particle. Conversely, in expressions (1.2), we begin with what we once regarded as purely a particle—say, an electron—and we associate its corpuscular characteristics E and p with the wave characteristics f and of the corresponding wave.
    [Show full text]
  • Quantum Aspects of Life / Editors, Derek Abbott, Paul C.W
    Quantum Aspectsof Life P581tp.indd 1 8/18/08 8:42:58 AM This page intentionally left blank foreword by SIR ROGER PENROSE editors Derek Abbott (University of Adelaide, Australia) Paul C. W. Davies (Arizona State University, USAU Arun K. Pati (Institute of Physics, Orissa, India) Imperial College Press ICP P581tp.indd 2 8/18/08 8:42:58 AM Published by Imperial College Press 57 Shelton Street Covent Garden London WC2H 9HE Distributed by World Scientific Publishing Co. Pte. Ltd. 5 Toh Tuck Link, Singapore 596224 USA office: 27 Warren Street, Suite 401-402, Hackensack, NJ 07601 UK office: 57 Shelton Street, Covent Garden, London WC2H 9HE Library of Congress Cataloging-in-Publication Data Quantum aspects of life / editors, Derek Abbott, Paul C.W. Davies, Arun K. Pati ; foreword by Sir Roger Penrose. p. ; cm. Includes bibliographical references and index. ISBN-13: 978-1-84816-253-2 (hardcover : alk. paper) ISBN-10: 1-84816-253-7 (hardcover : alk. paper) ISBN-13: 978-1-84816-267-9 (pbk. : alk. paper) ISBN-10: 1-84816-267-7 (pbk. : alk. paper) 1. Quantum biochemistry. I. Abbott, Derek, 1960– II. Davies, P. C. W. III. Pati, Arun K. [DNLM: 1. Biogenesis. 2. Quantum Theory. 3. Evolution, Molecular. QH 325 Q15 2008] QP517.Q34.Q36 2008 576.8'3--dc22 2008029345 British Library Cataloguing-in-Publication Data A catalogue record for this book is available from the British Library. Photo credit: Abigail P. Abbott for the photo on cover and title page. Copyright © 2008 by Imperial College Press All rights reserved. This book, or parts thereof, may not be reproduced in any form or by any means, electronic or mechanical, including photocopying, recording or any information storage and retrieval system now known or to be invented, without written permission from the Publisher.
    [Show full text]
  • Qualification Exam: Quantum Mechanics
    Qualification Exam: Quantum Mechanics Name: , QEID#43228029: July, 2019 Qualification Exam QEID#43228029 2 1 Undergraduate level Problem 1. 1983-Fall-QM-U-1 ID:QM-U-2 Consider two spin 1=2 particles interacting with one another and with an external uniform magnetic field B~ directed along the z-axis. The Hamiltonian is given by ~ ~ ~ ~ ~ H = −AS1 · S2 − µB(g1S1 + g2S2) · B where µB is the Bohr magneton, g1 and g2 are the g-factors, and A is a constant. 1. In the large field limit, what are the eigenvectors and eigenvalues of H in the "spin-space" { i.e. in the basis of eigenstates of S1z and S2z? 2. In the limit when jB~ j ! 0, what are the eigenvectors and eigenvalues of H in the same basis? 3. In the Intermediate regime, what are the eigenvectors and eigenvalues of H in the spin space? Show that you obtain the results of the previous two parts in the appropriate limits. Problem 2. 1983-Fall-QM-U-2 ID:QM-U-20 1. Show that, for an arbitrary normalized function j i, h jHj i > E0, where E0 is the lowest eigenvalue of H. 2. A particle of mass m moves in a potential 1 kx2; x ≤ 0 V (x) = 2 (1) +1; x < 0 Find the trial state of the lowest energy among those parameterized by σ 2 − x (x) = Axe 2σ2 : What does the first part tell you about E0? (Give your answers in terms of k, m, and ! = pk=m). Problem 3. 1983-Fall-QM-U-3 ID:QM-U-44 Consider two identical particles of spin zero, each having a mass m, that are con- strained to rotate in a plane with separation r.
    [Show full text]
  • Molecular Energy Levels
    MOLECULAR ENERGY LEVELS DR IMRANA ASHRAF OUTLINE q MOLECULE q MOLECULAR ORBITAL THEORY q MOLECULAR TRANSITIONS q INTERACTION OF RADIATION WITH MATTER q TYPES OF MOLECULAR ENERGY LEVELS q MOLECULE q In nature there exist 92 different elements that correspond to stable atoms. q These atoms can form larger entities- called molecules. q The number of atoms in a molecule vary from two - as in N2 - to many thousand as in DNA, protiens etc. q Molecules form when the total energy of the electrons is lower in the molecule than in individual atoms. q The reason comes from the Aufbau principle - to put electrons into the lowest energy configuration in atoms. q The same principle goes for molecules. q MOLECULE q Properties of molecules depend on: § The specific kind of atoms they are composed of. § The spatial structure of the molecules - the way in which the atoms are arranged within the molecule. § The binding energy of atoms or atomic groups in the molecule. TYPES OF MOLECULES q MONOATOMIC MOLECULES § The elements that do not have tendency to form molecules. § Elements which are stable single atom molecules are the noble gases : helium, neon, argon, krypton, xenon and radon. q DIATOMIC MOLECULES § Diatomic molecules are composed of only two atoms - of the same or different elements. § Examples: hydrogen (H2), oxygen (O2), carbon monoxide (CO), nitric oxide (NO) q POLYATOMIC MOLECULES § Polyatomic molecules consist of a stable system comprising three or more atoms. TYPES OF MOLECULES q Empirical, Molecular And Structural Formulas q Empirical formula: Indicates the simplest whole number ratio of all the atoms in a molecule.
    [Show full text]
  • Atomic Excitation Potentials
    ATOMIC EXCITATION POTENTIALS PURPOSE In this lab you will study the excitation of mercury atoms by colliding electrons with the atoms, and confirm that this excitation requires a specific quantity of energy. THEORY In general, atoms of an element can exist in a number of either excited or ionized states, or the ground state. This lab will focus on electron collisions in which a free electron gives up just the amount of kinetic energy required to excite a ground state mercury atom into its first excited state. However, it is important to consider all other processes which constantly change the energy states of the atoms. An atom in the ground state may absorb a photon of energy exactly equal to the energy difference between the ground state and some excited state, whereas another atom may collide with an electron and absorb some fraction of the electron's kinetic energy which is the amount needed to put that atom in some excited state (collisional excitation). Each atom in an excited state then spontaneously emits a photon and drops from a higher excited state to a lower one (or to the ground state). Another possibility is that an atom may collide with an electron which carries away kinetic energy equal to the atomic excitation energy so that the atom ends up in, say, the ground state (collisional deexcitation). Lastly, an atom can be placed into an ionized state (one or more of its electrons stripped away) if the collision transfers energy greater than the ionization potential of the atom. Likewise an ionized atom can capture a free electron.
    [Show full text]
  • Theory and Experiment in the Quantum-Relativity Revolution
    Theory and Experiment in the Quantum-Relativity Revolution expanded version of lecture presented at American Physical Society meeting, 2/14/10 (Abraham Pais History of Physics Prize for 2009) by Stephen G. Brush* Abstract Does new scientific knowledge come from theory (whose predictions are confirmed by experiment) or from experiment (whose results are explained by theory)? Either can happen, depending on whether theory is ahead of experiment or experiment is ahead of theory at a particular time. In the first case, new theoretical hypotheses are made and their predictions are tested by experiments. But even when the predictions are successful, we can’t be sure that some other hypothesis might not have produced the same prediction. In the second case, as in a detective story, there are already enough facts, but several theories have failed to explain them. When a new hypothesis plausibly explains all of the facts, it may be quickly accepted before any further experiments are done. In the quantum-relativity revolution there are examples of both situations. Because of the two-stage development of both relativity (“special,” then “general”) and quantum theory (“old,” then “quantum mechanics”) in the period 1905-1930, we can make a double comparison of acceptance by prediction and by explanation. A curious anti- symmetry is revealed and discussed. _____________ *Distinguished University Professor (Emeritus) of the History of Science, University of Maryland. Home address: 108 Meadowlark Terrace, Glen Mills, PA 19342. Comments welcome. 1 “Science walks forward on two feet, namely theory and experiment. ... Sometimes it is only one foot which is put forward first, sometimes the other, but continuous progress is only made by the use of both – by theorizing and then testing, or by finding new relations in the process of experimenting and then bringing the theoretical foot up and pushing it on beyond, and so on in unending alterations.” Robert A.
    [Show full text]
  • 15.1 Excited State Processes
    15.1 Excited State Processes • both optical and dark processes are described in order to develop a kinetic picture of the excited state • the singlet-triplet split and Stoke's shift determine the wavelengths of emission • the fluorescence quantum yield and lifetime depend upon the relative rates of optical and dark processes • excited states can be quenched by other molecules in the solution 15.1 : 1/8 Excited State Processes Involving Light • absorption occurs over one cycle of light, i.e. 10-14 to 10-15 s • fluorescence is spin allowed and occurs over a time scale of 10-9 to 10-7 s • in fluid solution, fluorescence comes from the lowest energy singlet state S2 •the shortest wavelength in the T2 fluorescence spectrum is the longest S1 wavelength in the absorption spectrum T1 • triplet states lie at lower energy than their corresponding singlet states • phosphorescence is spin forbidden and occurs over a time scale of 10-3 to 1 s • you can estimate where spectral features will be located by assuming that S0 absorption, fluorescence and phosphorescence occur one color apart - thus a yellow solution absorbs in the violet, fluoresces in the blue and phosphoresces in the green 15.1 : 2/8 Excited State Dark Processes • excess vibrational energy can be internal conversion transferred to the solvent with very few S2 -13 -11 vibrations (10 to 10 s) - this T2 process is called vibrational relaxation S1 • a molecule in v = 0 of S2 can convert T1 iso-energetically to a higher vibrational vibrational relaxation intersystem level of S1 - this is called
    [Show full text]
  • Frontiers of Quantum and Mesoscopic Thermodynamics 14 - 20 July 2019, Prague, Czech Republic
    Frontiers of Quantum and Mesoscopic Thermodynamics 14 - 20 July 2019, Prague, Czech Republic Under the auspicies of Ing. Miloš Zeman President of the Czech Republic Jaroslav Kubera President of the Senate of the Parliament of the Czech Republic Milan Štˇech Vice-President of the Senate of the Parliament of the Czech Republic Prof. RNDr. Eva Zažímalová, CSc. President of the Czech Academy of Sciences Dominik Cardinal Duka OP Archbishop of Prague Supported by • Committee on Education, Science, Culture, Human Rights and Petitions of the Senate of the Parliament of the Czech Republic • Institute of Physics, the Czech Academy of Sciences • Department of Physics, Texas A&M University, USA • Institute for Theoretical Physics, University of Amsterdam, The Netherlands • College of Engineering and Science, University of Detroit Mercy, USA • Quantum Optics Lab at the BRIC, Baylor University, USA • Institut de Physique Théorique, CEA/CNRS Saclay, France Topics • Non-equilibrium quantum phenomena • Foundations of quantum physics • Quantum measurement, entanglement and coherence • Dissipation, dephasing, noise and decoherence • Many body physics, quantum field theory • Quantum statistical physics and thermodynamics • Quantum optics • Quantum simulations • Physics of quantum information and computing • Topological states of quantum matter, quantum phase transitions • Macroscopic quantum behavior • Cold atoms and molecules, Bose-Einstein condensates • Mesoscopic, nano-electromechanical and nano-optical systems • Biological systems, molecular motors and
    [Show full text]
  • On the Logic Resolution of the Wave Particle Duality Paradox in Quantum Mechanics (Extended Abstract) M.A
    On the logic resolution of the wave particle duality paradox in quantum mechanics (Extended abstract) M.A. Nait Abdallah To cite this version: M.A. Nait Abdallah. On the logic resolution of the wave particle duality paradox in quantum me- chanics (Extended abstract). 2016. hal-01303223 HAL Id: hal-01303223 https://hal.archives-ouvertes.fr/hal-01303223 Preprint submitted on 18 Apr 2016 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. On the logic resolution of the wave particle duality paradox in quantum mechanics (Extended abstract) M.A. Nait Abdallah UWO, London, Canada and INRIA, Paris, France Abstract. In this paper, we consider three landmark experiments of quantum physics and discuss the related wave particle duality paradox. We present a formalization, in terms of formal logic, of single photon self- interference. We show that the wave particle duality paradox appears, from the logic point of view, in the form of two distinct fallacies: the hard information fallacy and the exhaustive disjunction fallacy. We show that each fallacy points out some fundamental aspect of quantum physical systems and we present a logic solution to the paradox.
    [Show full text]