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Yes, More Decoherence: a Reply to Critics
Yes, More Decoherence: A Reply to Critics Elise M. Crull∗ Submitted 11 July 2017; revised 24 August 2017 1 Introduction A few years ago I published an article in this journal titled \Less interpretation and more decoherence in quantum gravity and inflationary cosmology" (Crull, 2015) that generated replies from three pairs of authors: Vassallo and Esfeld (2015), Okon and Sudarsky (2016) and Fortin and Lombardi (2017). As a philosopher of physics it is my chief aim to engage physicists and philosophers alike in deeper conversation regarding scientific theories and their implications. In as much as my earlier paper provoked a suite of responses and thereby brought into sharper relief numerous misconceptions regarding decoherence, I welcome the occasion provided by the editors of this journal to continue the discussion. In what follows, I respond to my critics in some detail (wherein the devil is often found). I must be clear at the outset, however, that due to the nature of these criticisms, much of what I say below can be categorized as one or both of the following: (a) a repetition of points made in the original paper, and (b) a reiteration of formal and dynamical aspects of quantum decoherence considered uncontroversial by experts working on theoretical and experimental applications of this process.1 I begin with a few paragraphs describing what my 2015 paper both was, and was not, about. I then briefly address Vassallo's and Esfeld's (hereafter VE) relatively short response to me, dedicating the bulk of my reply to the lengthy critique of Okon and Sudarsky (hereafter OS). -
1 Postulate (QM4): Quantum Measurements
Part IIC Lent term 2019-2020 QUANTUM INFORMATION & COMPUTATION Nilanjana Datta, DAMTP Cambridge 1 Postulate (QM4): Quantum measurements An isolated (closed) quantum system has a unitary evolution. However, when an exper- iment is done to find out the properties of the system, there is an interaction between the system and the experimentalists and their equipment (i.e., the external physical world). So the system is no longer closed and its evolution is not necessarily unitary. The following postulate provides a means of describing the effects of a measurement on a quantum-mechanical system. In classical physics the state of any given physical system can always in principle be fully determined by suitable measurements on a single copy of the system, while leaving the original state intact. In quantum theory the corresponding situation is bizarrely different { quantum measurements generally have only probabilistic outcomes, they are \invasive", generally unavoidably corrupting the input state, and they reveal only a rather small amount of information about the (now irrevocably corrupted) input state identity. Furthermore the (probabilistic) change of state in a quantum measurement is (unlike normal time evolution) not a unitary process. Here we outline the associated mathematical formalism, which is at least, easy to apply. (QM4) Quantum measurements and the Born rule In Quantum Me- chanics one measures an observable, i.e. a self-adjoint operator. Let A be an observable acting on the state space V of a quantum system Since A is self-adjoint, its eigenvalues P are real. Let its spectral projection be given by A = n anPn, where fang denote the set of eigenvalues of A and Pn denotes the orthogonal projection onto the subspace of V spanned by eigenvectors of A corresponding to the eigenvalue Pn. -
Introduction Physics Engines AGEIA Physx SDK AGEIA
25/3/2008 SVR2007 Introduction Tutorial AGEIA PhysX • What does physics give? – Real world interaction metaphor – Realistic simulation Virtual Reality • Who needs physics? and Multimedia { mouse, ds2, gsm, masb, vt, jk } @cin.ufpe.br Research Group Thiago Souto Maior – Immersive games and applications Daliton Silva Guilherme Moura Márcio Bueno • How to use this? Veronica Teichrieb Judith Kelner – Through physics engines implemented in software or hardware Petrópolis, May 2007 Physics Engines AGEIA PhysX SDK • Simplified Newtonian models • Based upon NovodeX API • “High precision” versus “real time” simulations • Commercial and open source engines • Middleware concept • What comes together in a physics engine? • First asynchronous physics API – Mandatory • Tons of math calculations • Takes advantage of multiprocessing game • Collision detection • Rigid body dynamics systems – Optional • Fluid dynamics • Cloth simulation • Particle systems • Deformable object dynamics AGEIA PhysX SDK AGEIA PhysX SDK • Supports game • Integration with game development life cycle engines – 3DSMax and Maya – Unreal Engine 3.0 plugins (PhysX – Emergent GameBryo Create) – Natural Motion – Properties tuning with Endorphin PhysX Rocket • Runs in PC, Xbox 360 – Visual remote and PS3 debugging with PhysX VRD 1 25/3/2008 AGEIA PhysX SDK AGEIA PhysX Processor • Supports • AGEIA PhysX PPU – Complex rigid body dynamics • Powerful PPU + – Collision detection CPU + GPU – Joints and springs – Physics + Math + – Volumetric fluid simulation Fast Rendering – Particle systems -
Quantum Circuits with Mixed States Is Polynomially Equivalent in Computational Power to the Standard Unitary Model
Quantum Circuits with Mixed States Dorit Aharonov∗ Alexei Kitaev† Noam Nisan‡ February 1, 2008 Abstract Current formal models for quantum computation deal only with unitary gates operating on “pure quantum states”. In these models it is difficult or impossible to deal formally with several central issues: measurements in the middle of the computation; decoherence and noise, using probabilistic subroutines, and more. It turns out, that the restriction to unitary gates and pure states is unnecessary. In this paper we generalize the formal model of quantum circuits to a model in which the state can be a general quantum state, namely a mixed state, or a “density matrix”, and the gates can be general quantum operations, not necessarily unitary. The new model is shown to be equivalent in computational power to the standard one, and the problems mentioned above essentially disappear. The main result in this paper is a solution for the subroutine problem. The general function that a quantum circuit outputs is a probabilistic function. However, the question of using probabilistic functions as subroutines was not previously dealt with, the reason being that in the language of pure states, this simply can not be done. We define a natural notion of using general subroutines, and show that using general subroutines does not strengthen the model. As an example of the advantages of analyzing quantum complexity using density ma- trices, we prove a simple lower bound on depth of circuits that compute probabilistic func- arXiv:quant-ph/9806029v1 8 Jun 1998 tions. Finally, we deal with the question of inaccurate quantum computation with mixed states. -
The Era of Carbon Allotropes Andreas Hirsch
commentary The era of carbon allotropes Andreas Hirsch Twenty-five years on from the discovery of 60C , the outstanding properties and potential applications of the synthetic carbon allotropes — fullerenes, nanotubes and graphene — overwhelmingly illustrate their unique scientific and technological importance. arbon is the element in the periodic consist of extended networks of sp3- and 1985, with the advent of fullerenes (Fig. 1), table that provides the basis for life sp2 -hybridized carbon atoms, respectively. which were observed for the first time by Con Earth. It is also important for Both forms show unique physical properties Kroto et al.3. This serendipitous discovery many technological applications, ranging such as hardness, thermal conductivity, marked the beginning of an era of synthetic from drugs to synthetic materials. This lubrication behaviour or electrical carbon allotropes. Now, as we celebrate role is a consequence of carbon’s ability conductivity. Conceptually, many other buckminsterfullerene’s 25th birthday, it is to bind to itself and to nearly all elements ways to construct carbon allotropes are also the time to reflect on a growing family in almost limitless variety. The resulting possible by altering the periodic binding of synthetic carbon allotropes, which structural diversity of organic compounds motif in networks consisting of sp3-, sp2- includes the synthesis of carbon nanotubes and molecules is accompanied by a broad and sp-hybridized carbon atoms1,2. As a in 19914 and the rediscovery of graphene range of -
Qiskit Backend Specifications for Openqasm and Openpulse
Qiskit Backend Specifications for OpenQASM and OpenPulse Experiments David C. McKay1,∗ Thomas Alexander1, Luciano Bello1, Michael J. Biercuk2, Lev Bishop1, Jiayin Chen2, Jerry M. Chow1, Antonio D. C´orcoles1, Daniel Egger1, Stefan Filipp1, Juan Gomez1, Michael Hush2, Ali Javadi-Abhari1, Diego Moreda1, Paul Nation1, Brent Paulovicks1, Erick Winston1, Christopher J. Wood1, James Wootton1 and Jay M. Gambetta1 1IBM Research 2Q-CTRL Pty Ltd, Sydney NSW Australia September 11, 2018 Abstract As interest in quantum computing grows, there is a pressing need for standardized API's so that algorithm designers, circuit designers, and physicists can be provided a common reference frame for designing, executing, and optimizing experiments. There is also a need for a language specification that goes beyond gates and allows users to specify the time dynamics of a quantum experiment and recover the time dynamics of the output. In this document we provide a specification for a common interface to backends (simulators and experiments) and a standarized data structure (Qobj | quantum object) for sending experiments to those backends via Qiskit. We also introduce OpenPulse, a language for specifying pulse level control (i.e. control of the continuous time dynamics) of a general quantum device independent of the specific arXiv:1809.03452v1 [quant-ph] 10 Sep 2018 hardware implementation. ∗[email protected] 1 Contents 1 Introduction3 1.1 Intended Audience . .4 1.2 Outline of Document . .4 1.3 Outside of the Scope . .5 1.4 Interface Language and Schemas . .5 2 Qiskit API5 2.1 General Overview of a Qiskit Experiment . .7 2.2 Provider . .8 2.3 Backend . -
Pilot Quantum Error Correction for Global
Pilot Quantum Error Correction for Global- Scale Quantum Communications Laszlo Gyongyosi*1,2, Member, IEEE, Sandor Imre1, Member, IEEE 1Quantum Technologies Laboratory, Department of Telecommunications Budapest University of Technology and Economics 2 Magyar tudosok krt, H-1111, Budapest, Hungary 2Information Systems Research Group, Mathematics and Natural Sciences Hungarian Academy of Sciences H-1518, Budapest, Hungary *[email protected] Real global-scale quantum communications and quantum key distribution systems cannot be implemented by the current fiber and free-space links. These links have high attenuation, low polarization-preserving capability or extreme sensitivity to the environment. A potential solution to the problem is the space-earth quantum channels. These channels have no absorption since the signal states are propagated in empty space, however a small fraction of these channels is in the atmosphere, which causes slight depolarizing effect. Furthermore, the relative motion of the ground station and the satellite causes a rotation in the polarization of the quantum states. In the current approaches to compensate for these types of polarization errors, high computational costs and extra physical apparatuses are required. Here we introduce a novel approach which breaks with the traditional views of currently developed quantum-error correction schemes. The proposed solution can be applied to fix the polarization errors which are critical in space-earth quantum communication systems. The channel coding scheme provides capacity-achieving communication over slightly depolarizing space-earth channels. I. Introduction Quantum error-correction schemes use different techniques to correct the various possible errors which occur in a quantum channel. In the first decade of the 21st century, many revolutionary properties of quantum channels were discovered [12-16], [19-22] however the efficient error- correction in quantum systems is still a challenge. -
Quantum Noise in Quantum Optics: the Stochastic Schr\" Odinger
Quantum Noise in Quantum Optics: the Stochastic Schr¨odinger Equation Peter Zoller † and C. W. Gardiner ∗ † Institute for Theoretical Physics, University of Innsbruck, 6020 Innsbruck, Austria ∗ Department of Physics, Victoria University Wellington, New Zealand February 1, 2008 arXiv:quant-ph/9702030v1 12 Feb 1997 Abstract Lecture Notes for the Les Houches Summer School LXIII on Quantum Fluc- tuations in July 1995: “Quantum Noise in Quantum Optics: the Stochastic Schroedinger Equation” to appear in Elsevier Science Publishers B.V. 1997, edited by E. Giacobino and S. Reynaud. 0.1 Introduction Theoretical quantum optics studies “open systems,” i.e. systems coupled to an “environment” [1, 2, 3, 4]. In quantum optics this environment corresponds to the infinitely many modes of the electromagnetic field. The starting point of a description of quantum noise is a modeling in terms of quantum Markov processes [1]. From a physical point of view, a quantum Markovian description is an approximation where the environment is modeled as a heatbath with a short correlation time and weakly coupled to the system. In the system dynamics the coupling to a bath will introduce damping and fluctuations. The radiative modes of the heatbath also serve as input channels through which the system is driven, and as output channels which allow the continuous observation of the radiated fields. Examples of quantum optical systems are resonance fluorescence, where a radiatively damped atom is driven by laser light (input) and the properties of the emitted fluorescence light (output)are measured, and an optical cavity mode coupled to the outside radiation modes by a partially transmitting mirror. -
Carbon Allotropes
LABORATORIES Lab- Carbon Allotropes Background: Carbon occurs in several different forms known as allotropes. These allotropes are characterized by differences in bonding patterns which result in substances with distinctly different properties. The three allotropes that will be studied in this lab are: graphite, diamond and fullerene. Diamonds are a colorless, crystalline solid where each carbon atom is bonded to four others in a network pattern. This bonding structure makes diamond the hardest material known. Graphite is a soft , black crystalline solid of carbon where the carbon atoms are bonded together in layers. Within each layer, each carbon atom is bonded to 3 other carbon atoms. Because the adjacent layers are held together by weak London dispersion forces graphite is very soft. The most recently discovered allotrope of carbon is the fullerene. Fullerenes are a cage like spherical structure of bonded carbon atoms. The fullerene bonding pattern resembles a soccer ball. Fullerene particles are also referred to as nanoparticles and are being explored for a variety of applications. Objective: Students will be able to: 1. Describe how elements can exist as 2 or more different structures. 2. Distinguish between different allotropes based on structural analysis and properties. 3. Analyze how the bonding structure could influence the properties. 4. Distinguish between crystalline and amorphous structures. 5. Compare and contrast the 3 different carbon allotropes. Materials: Molecular model kits digital camera Procedure: 1. Students at each lab table will work as a group using 3 model sets. 2. Build two sheets of graphite using 15 carbon atoms for each sheet 3. Take a digital picture of the model created and include it in your report 4. -
On Photodynamic Therapy of Alzheimer's Disease Using
Journal of Scientific Research & Reports 2(1): 206-227, 2013; Article no. JSRR.2013.015 SCIENCEDOMAIN international www.sciencedomain.org On Photodynamic Therapy of Alzheimer’s Disease Using Intrathecal Nanorobot Drug Delivery of Curcuma Longa for Enhanced Bioavailability Kal Renganathan Sharma 1* 1Lone Star College University Park20515 State Hwy 249 Houston, TX77070, USA. Author’s Contribution The only author performed the whole research work. Author KRS wrote the first draft of the paper. Author KRS read and approved the final manuscript. Received 28 th December 2012 th Research Article Accepted 19 February 2013 Published 22nd March 2013 ABSTRACT Robotics was first instructed as a collegiate course about 20 years ago at Stanford University, Stanford, CA. From the first IRB6 the electrically powered robot in 1974 over a 30 year period the industry has grown. A leading supplier of robots has put out over 100,000 robots by year 2001. Robot capable of handling 500 kg load was introduced in 2001, IRB 7000. A number of advances have been made in nanostructuring. About 40 different nanostructuring methods were reviewed recently [2]. Nanorobots can be developed that effect cures of disorders that are difficult to treat. Principles from photodynamic therapy, fullerene chemistry, nanostructuring, x-rays, computers, pharmacokinetics and robotics are applied in developing a strategy for nanorobot, treatment of Alzheimer’s disease. The curcuma longa that has shown curative effects in rats’ brain with Alzheimers is complexed with fullerenes. The drug is inactive when caged. It is infused intrathecallyinto the cerebrospinal system. Irradiation of the hypothalamous and other areas of the brain where Alzheimer’s disease is prevalent lead to breakage of fullerenes and availability of the drug with the diseased cells. -
Quantum Computation and Complexity Theory
Quantum computation and complexity theory Course given at the Institut fÈurInformationssysteme, Abteilung fÈurDatenbanken und Expertensysteme, University of Technology Vienna, Wintersemester 1994/95 K. Svozil Institut fÈur Theoretische Physik University of Technology Vienna Wiedner Hauptstraûe 8-10/136 A-1040 Vienna, Austria e-mail: [email protected] December 5, 1994 qct.tex Abstract The Hilbert space formalism of quantum mechanics is reviewed with emphasis on applicationsto quantum computing. Standardinterferomeric techniques are used to construct a physical device capable of universal quantum computation. Some consequences for recursion theory and complexity theory are discussed. hep-th/9412047 06 Dec 94 1 Contents 1 The Quantum of action 3 2 Quantum mechanics for the computer scientist 7 2.1 Hilbert space quantum mechanics ..................... 7 2.2 From single to multiple quanta Ð ªsecondº ®eld quantization ...... 15 2.3 Quantum interference ............................ 17 2.4 Hilbert lattices and quantum logic ..................... 22 2.5 Partial algebras ............................... 24 3 Quantum information theory 25 3.1 Information is physical ........................... 25 3.2 Copying and cloning of qbits ........................ 25 3.3 Context dependence of qbits ........................ 26 3.4 Classical versus quantum tautologies .................... 27 4 Elements of quantum computatability and complexity theory 28 4.1 Universal quantum computers ....................... 30 4.2 Universal quantum networks ........................ 31 4.3 Quantum recursion theory ......................... 35 4.4 Factoring .................................. 36 4.5 Travelling salesman ............................. 36 4.6 Will the strong Church-Turing thesis survive? ............... 37 Appendix 39 A Hilbert space 39 B Fundamental constants of physics and their relations 42 B.1 Fundamental constants of physics ..................... 42 B.2 Conversion tables .............................. 43 B.3 Electromagnetic radiation and other wave phenomena ......... -
Qubit Coupled Cluster Singles and Doubles Variational Quantum Eigensolver Ansatz for Electronic Structure Calculations
Quantum Science and Technology PAPER Qubit coupled cluster singles and doubles variational quantum eigensolver ansatz for electronic structure calculations To cite this article: Rongxin Xia and Sabre Kais 2020 Quantum Sci. Technol. 6 015001 View the article online for updates and enhancements. This content was downloaded from IP address 128.210.107.25 on 20/10/2020 at 12:02 Quantum Sci. Technol. 6 (2021) 015001 https://doi.org/10.1088/2058-9565/abbc74 PAPER Qubit coupled cluster singles and doubles variational quantum RECEIVED 27 July 2020 eigensolver ansatz for electronic structure calculations REVISED 14 September 2020 Rongxin Xia and Sabre Kais∗ ACCEPTED FOR PUBLICATION Department of Chemistry, Department of Physics and Astronomy, and Purdue Quantum Science and Engineering Institute, Purdue 29 September 2020 University, West Lafayette, United States of America ∗ PUBLISHED Author to whom any correspondence should be addressed. 20 October 2020 E-mail: [email protected] Keywords: variational quantum eigensolver, electronic structure calculations, unitary coupled cluster singles and doubles excitations Abstract Variational quantum eigensolver (VQE) for electronic structure calculations is believed to be one major potential application of near term quantum computing. Among all proposed VQE algorithms, the unitary coupled cluster singles and doubles excitations (UCCSD) VQE ansatz has achieved high accuracy and received a lot of research interest. However, the UCCSD VQE based on fermionic excitations needs extra terms for the parity when using Jordan–Wigner transformation. Here we introduce a new VQE ansatz based on the particle preserving exchange gate to achieve qubit excitations. The proposed VQE ansatz has gate complexity up-bounded to O(n4)for all-to-all connectivity where n is the number of qubits of the Hamiltonian.