Local and Distributed Quantum Computation
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Physicists Set New Records for Silicon Quantum Computing 12 October 2014
Physicists set new records for silicon quantum computing 12 October 2014 been published simultaneously today in the journal Nature Nanotechnology. "For quantum computing to become a reality we need to operate the bits with very low error rates," says Scientia Professor Andrew Dzurak, who is Director of the Australian National Fabrication Facility at UNSW, where the devices were made. "We've now come up with two parallel pathways for building a quantum computer in silicon, each of which shows this super accuracy," adds Associate Professor Andrea Morello from UNSW's School of Electrical Engineering and Telecommunications. The UNSW teams, which are also affiliated with the ARC Centre of Excellence for Quantum Computation & Communication Technology, were first in the world to demonstrate single-atom spin qubits in silicon, reported in Nature in 2012 and 2013. Now the team led by Dzurak has discovered a way to create an "artificial atom" qubit with a device remarkably similar to the silicon transistors used in This is an artist impression of an electron wave function consumer electronics, known as MOSFETs. Post- (blue), confined in a crystal of nuclear-spin-free doctoral researcher Menno Veldhorst, lead author 28-silicon atoms (black), controlled by a nanofabricated on the paper reporting the artificial atom qubit, metal gate (silver). The spin of the electron encodes a says, "It is really amazing that we can make such long-lived, high fidelity quantum bit. Credit: Dr Stephanie an accurate qubit using pretty much the same Simmons, UNSW Australia. devices as we have in our laptops and phones". Meanwhile, Morello's team has been pushing the "natural" phosphorus atom qubit to the extremes of Two research teams working in the same performance. -
Quantifying the Quantum Gate Fidelity of Single-Atom Spin Qubits in Silicon
Quantifying the quantum gate fidelity of single-atom spin qubits in silicon by randomized benchmarking J T Muhonen,1, ∗ A Laucht,1 S Simmons,1 J P Dehollain,1 R Kalra,1 F E Hudson,1 S Freer,1 K M Itoh,2 D N Jamieson,3 J C McCallum,3 A S Dzurak,1 and A Morello1, y 1Centre for Quantum Computation and Communication Technology, School of Electrical Engineering and Telecommunications, UNSW Australia, Sydney, New South Wales 2052, Australia 2School of Fundamental Science and Technology, Keio University, 3-14-1 Hiyoshi, 223-8522, Japan 3Centre for Quantum Computation and Communication Technology, School of Physics, University of Melbourne, Melbourne, Victoria 3010, Australia Building upon the demonstration of coherent control and single-shot readout of the electron and nuclear spins of individual 31P atoms in silicon, we present here a systematic experimental estimate of quantum gate fidelities using randomized benchmarking of 1-qubit gates in the Clifford group. We apply this analysis to the electron and the ionized 31P nucleus of a single P donor in isotopically purified 28Si. We find average gate fidelities of 99.95% for the electron, and 99.99% for the nuclear spin. These values are above certain error correction thresholds, and demonstrate the potential of donor-based quantum computing in silicon. By studying the influence of the shape and power of the control pulses, we find evidence that the present limitation to the gate fidelity is mostly related to the external hardware, and not the intrinsic behaviour of the qubit. I. INTRODUCTION number of qubits since the number of measurements re- quired to completely map a multi-qubit process increases The discovery of quantum error correction is among exponentially with the number of qubits involved. -
Nuclear Spin, I |
Sensing & Controlling Single Spins in Silicon Andrew Dzurak University of New South Wales [email protected] ANFF – AFOSR Program Review Washington D.C., 30 April - 4 May 2012 ANFF @ UNSW • 3 x EBL Systems (Raith, FEI ...) • Highest Concentration in Australia • Sub-10nm Features • Silicon MOS Process Line TiAuPd ANFF-NSW: Key Research Areas Silicon Nanoelectronics Silicon Photovoltaics Biomedical Devices (eg. Bionics, Si Biosensors) Telecomms (Nano-photonics) Quantum Information Technologies www.anff.org.au Conventional computing … … must confront some serious issues Cost of Fab $60B $50B $40B 360B $20B ? $10B $0B 1992 1995 1998 2001 2004 2007 2010 Year Quantum computing … could well be the solution Conventional Quantum |1> Computer Computer 0 , 1 |0 >, |1 > |0> bits qubits Quantum state of a two-level system |0> |1> Quantum Information Science Data Security Decryption National Security National Security Financial Services Intelligence e-Commerce Killer? Apps High Performance Semiconductors Computing Database Searching Integrated Circuits Bioinformatics Sensors Modeling & Design Nano-structuring Code Decryption • Public key encryption (RSA-129) is (almost) uncrackable. Basis of public secure comms today • A full-scale (few hundred qubits) quantum computer could crack RSA-129 in seconds (Peter Shor – 1994) • Obvious applications in national and global security High Performance Computing • Simulation (modeling) & database searching • Existing supercomputers now under strain • Application areas: Nuclear weapons simulation Rapid data -
High-Fidelity Readout and Control of a Nuclear Spin Qubit in Silicon
1 High-fidelity readout and control of a nuclear spin qubit in silicon Jarryd J. Pla1, Kuan Y. Tan1†, Juan P. Dehollain1, Wee H. Lim1†, John J. L. Morton2, Floris A. Zwanenburg1†, David N. Jamieson3, Andrew S. Dzurak1, Andrea Morello1 1Centre for Quantum Computation and Communication Technology, School of Electrical Engineering & Telecommunications, University of New South Wales, Sydney, New South Wales 2052, Australia. 2London Centre for Nanotechnology, University College London, London WC1H 0AH, UK. 3Centre for Quantum Computation and Communication Technology, School of Physics, University of Melbourne, Melbourne, Victoria 3010, Australia. †Present addresses: Department of Applied Physics/COMP, Aalto University, P.O. Box 13500, FI-00076 AALTO, Finland (K.Y.T.); Asia Pacific University of Technology and Innovation, Technology Park Malaysia, Bukit Jalil, 57000 Kuala Lumpur, Malaysia (W.H.L.); NanoElectronics Group, MESA+ Institute for Nanotechnology, University of Twente, Enschede, The Netherlands (F.A.Z.). A single nuclear spin holds the promise of being a long-lived quantum bit or quantum memory, with the high fidelities required for fault-tolerant quantum computing. We show here that such promise could be fulfilled by a single phosphorus (31P) nuclear spin in a silicon nanostructure. By integrating single-shot readout of the electron spin with on-chip electron spin resonance, we demonstrate the quantum non-demolition, electrical single-shot readout of the nuclear spin, with readout fidelity better than 99.8% - the highest for any solid-state qubit. The single nuclear spin is then operated as a qubit by applying coherent radiofrequency (RF) pulses. For an ionized 31P donor we find a nuclear spin coherence time of 60 ms and a 1-qubit gate control fidelity exceeding 98%. -
Hybrid Qubits Solve Key Hurdle to Quantum Computing 28 December 2018
Hybrid qubits solve key hurdle to quantum computing 28 December 2018 In 1998, Daniel Loss, one of the authors of the current study, came up with a proposal, along with David DiVincenzo of IBM, to build a quantum computer by using the spins of electrons embedded in a quantum dot—a small particle that behaves like an atom, but that can be manipulated, so that they are sometimes called "artificial atoms." In the time since then, Loss and his team have endeavored to build practical devices. There are a number of barriers to developing practical devices in terms of speed. First, the device must be able to be initialized quickly. Initialization is the process of putting a qubit into a certain state, and if that cannot be done rapidly it slows down the device. Second, it must maintain coherence for a time long enough to make a measurement. Coherence refers to the Schematic of the device. Credit: RIKEN entanglement between two quantum states, and ultimately this is used to make the measurement, so if qubits become decoherent due to environmental noise, for example, the device Spin-based quantum computers have the potential becomes worthless. And finally, the ultimate state to tackle difficult mathematical problems that of the qubit must be able to be quickly read out. cannot be solved using ordinary computers, but many problems remain in making these machines While a number of methods have been proposed scalable. Now, an international group of for building a quantum computer, the one proposed researchers led by the RIKEN Center for Emergent by Loss and DiVincenzo remains one of the most Matter Science have crafted a new architecture for practically feasible, as it is based on quantum computing. -
The Quantum Times) in Producing the First in Their List of Guidelines Nor Was It Reported As Operating Laser, Are All Interesting and Enlightening
TThhee QQuuaannttuumm TTiimmeess APS Topical Group on Quantum Information, Concepts, and Computation Summer 2007 Volume 2, Number 2 Advances & Challenges in Quantum Key Distribution Quantum Key Distribution (QKD) is the flagship success of quantum communication. Since Bennett and Brassard’s 1984 publication [2] it has given a new direction to the field. (For a review see e.g. [3].) Up to then in quantum communication, the properties of quantum mechanics were used, for example, to improve on the through-put of optical channels. With the arrival of QKD an application has been created that achieves what Inside… cannot be achieved with classical communication alone: … you will find a little bit of provably secure protocols with no assumption about the everything. We begin with an computational power of an adversary. (This scenario is referred article from Norbert Lütkenhaus on to as unconditional security, a technical term in cryptography. quantum key distribution (QKD) Still, the devices of sender and receiver are assumed to be that grew out of a news article from perfect and out of bound of the adversary, an assumption without our last issue. Norbert speaks from which no cryptography is possible at all.) It is sufficient to the standpoint of someone at the prepare non-orthogonal states as signals and to measure them at forefront of quantum cryptography the receiver’s end. Then, using an authenticated public channel, and his article should be read by both parties can distill a secret key from the data. The procedure anyone interested in the current needs to be kick-started with some secret key in order to state and future direction of QKD. -
Issues in Physics & Astronomy
Issues in Physics & Astronomy Board on Physics and Astronomy • The National Academies • Washington, D.C. • 202-334-3520 • national-academies.org/bpa • Summer 2008 Understanding the Impact of Selling the Helium Reserve Michael H. Moloney, BPA Staff nder the sponsorship of the monatomic element, it passes easily containing 0.3 percent helium is consid- Bureau of Land Management at through tiny orifices and is therefore used ered economically viable. A few gas Uthe Department of the Interior, for leak detection in many scientific and deposits contain as much as 8 percent the BPA, in cooperation with the Na- technical applications. Its density is only helium. By comparison, the atmosphere tional Materials Advisory Board, has 15 percent that of air, making it useful as a contains only about 0.0005 percent. He- initiated a study to understand the lifting gas for aerostats and other devices. lium from wells that produce impact on the scientific community of Its high heat capacity, along with its uneconomically low concentrations, or the continuing sale of the U.S. helium inertness, makes it the preferred quench- from wells that produce higher concentra- reserve and recent developments in the ing medium for many applications in tions but do not flow through an extrac- helium market. materials processing, such as the produc- tion plant, is often vented to the atmo- The element helium has unique tion of high-quality superalloy powders. It sphere when the natural gas is burned. A properties. Liquefying near absolute is the preferred carrier gas for gas chroma- relatively minor amount of helium also is zero, it is the only option for many tography, a widely applied technique for vented at extraction plants that have no cryogenic applications, such as cooling chemical separations. -
FAHD A. MOHIYADDIN Quantum Computing Institute
FAHD A. MOHIYADDIN Quantum Computing Institute, Computational Sciences & Engineering Division, Oak Ridge National Laboratory, Tennessee, USA Email : [email protected] Phone: +1-865-237-7242 CAREER PROFILE . Postdoctoral research associate focused at designing quantum devices with Technology CAD and atomistic techniques. Extensive software skills developed with semiconductor modeling, programming microcontrollers and implementing image processing algorithms. Proven ability to adapt and work on diverse projects in academia and industry. Aim to work in a challenging, R&D based dynamic environment with an organization that values hard work, integrity and creativity. EDUCATION Doctor of Philosophy (Electrical Engineering) Mar 2011 – Nov 2014 University of New South Wales (UNSW), Australia Thesis Title: Designing a large scale quantum computer with classical & quantum simulations. Synopsis of Research: My research focused on the designing novel devices, in a team that performs world leading research, to develop a fully scalable quantum computer in silicon. Extensive modeling of a wide range of experimental devices was carried out, emphasizing their operation at the nanoscale quantum regime. They include single donor qubits, quantum dots, exchange coupled donor-pairs and many-body spin systems. Device parameters – such as defects, capacitances, electric fields & band-structure – were completely described and perfectly matched to fabricated devices, including the world’s first quantum bit in silicon. Based on close agreement with experiments, required device topologies and operation methods were proposed, for realizing the next generation of solid state quantum computer devices. Research resulted in 6 journal articles & 2 conference papers. Presented 3 talks and 9 posters at international conferences, and won 2 best poster awards. Collaborated with leading groups at Purdue University, University of Melbourne & University of Maryland. -
Topological Phases and Applications to Quantum Information Processing" ______List of Organizers
Proposed title: "Topological Phases and Applications to Quantum Information Processing" __________________________________________________________ List of organizers: Nicholas E. Bonesteel (Florida State University and NHMFL) Phone: (850) 644-7805, E-mail: [email protected] James P. Eisenstein (Caltech) Phone: (626) 395-4649, E-mail: [email protected] Michael H. Freedman (Microsoft Research) Phone: (805) 893-6313, E-mail: [email protected] Kirill Shtengel (UC Riverside) Phone: (951) 827-1058, E-mail: [email protected] Steven H. Simon (Lucent Technologies, Bell Labs) Phone: (908) 582-6006, E-mail: [email protected] __________________________________________________________ Proposed length: 4 weeks, preferably July 2 through July 29 or June 25 through July 22. However, anytime between June 18 and Sept 2, 2007 is acceptable. Pushing it toward earlier or later dates will result in conflicts with teaching for many of the potential attendees. __________________________________________________________ Abstract: Quantum computers, if realized in practice, promise exponential speed-up of some of the computational tasks that conventional classical algorithms are intrinsically incapable of handling efficiently. Perhaps even more intriguing possibility arises from being able to use quantum computers to simulate the behavior of other physical systems -- an exciting idea dating back to Feynman. Unfortunately, realizing a quantum computer in practice proves to be very difficult, chiefly due to the debilitating effects of decoherence plaguing all possible schemes which use microscopic degrees of freedom (such as nuclear or electronic spins) as basic building blocks. >From this perspective, topological quantum computing offers an attractive alternative by encoding quantum information in nonlocal topological degrees of freedom that are intrinsically protected from decoherence due to local noise. -
Quantum Computation with Spins in Quantum Dots
Quantum Computation With Spins In Quantum Dots Fikeraddis Damtie June 10, 2013 1 Introduction Physical implementation of quantum computating has been an active area of research since the last couple of decades. In classical computing, the transmission and manipulation of classical information is carried out by physical machines (computer hardwares, etc.). In theses machines the manipulation and transmission of information can be described using the laws of classical physics. Since Newtonian mechanics is a special limit of quantum mechanics, computers making use of the laws of quantum mechanics have greater computational power than classical computers. This need to create a powerful computing machine is the driving motor for research in the field of quantum computing. Until today, there are a few different schemes for implementing a quantum computer based on the David Divincenzo chriterias. Among these are: Spectral hole burning, Trapped ion, e-Helium, Gated qubits, Nuclear Magnetic Resonance, Optics, Quantum dots, Neutral atom, superconductors and doped silicon. In this project only the quantum dot scheme will be discussed. In the year 1997 Daniel Loss and David P.DiVincenzo proposed a spin-qubit quantum computer also called The Loss-DiVincenzo quantum computer. This proposal is now considered to be one of the most promising candidates for quantum computation in the solid state. The main idea of the proposal was to use the intrinsic spin-1=2 degrees of freedom of individual elecrons confined in semiconductor quantum dots. The proposal was made in a way to satisfy the five requirements for quantum computing by David diVincenzo which will be described in sec. -
Fast Noise-Resistant Control of Donor Nuclear Spin Qubits in Silicon
Fast noise-resistant control of donor nuclear spin qubits in silicon James Simon1;2, F. A. Calderon-Vargas2, Edwin Barnes2, and Sophia E. Economou2∗ 1Department of Physics, University of California, Berkeley, California 94720, USA 2Department of Physics, Virginia Tech, Blacksburg, Virginia 24061, USA A high degree of controllability and long coherence time make the nuclear spin of a phosphorus donor in isotopically purified silicon a promising candidate for a quantum bit. However, long- distance two-qubit coupling and fast, robust gates remain outstanding challenges for these systems. Here, following recent proposals for long-distance coupling via dipole-dipole interactions, we present a simple method to implement fast, high-fidelity arbitrary single- and two-qubit gates in the absence of charge noise. Moreover, we provide a method to make the single-qubit gates robust to moderate levels of charge noise to well within an error bound of 10−3. I. INTRODUCTION on clock transitions. Our approach is based on using optimally designed control pulse waveforms and energy Nuclear spins in the solid state present unparalleled transition modulation. Accordingly, we derive a time- advantages as a platform for quantum computing due independent analytical approximation for the system's to their long coherence times [1, 2] and high degree of Hamiltonian, explain how to rapidly implement arbi- controllability [3{5]. In particular, the nuclear spin of a trary, noise-resistant single-qubit gates with fidelities ex- phosphorus donor in silicon is a promising candidate for a ceeding 99.9% even in the presence of significant charge quantum bit [6, 7] owing to its coherent control [8{10] and noise, and provide a method to use the dipole-dipole in- minute-long coherence time [2]. -
Understanding and Suppressing Dephasing Noise in Semiconductor Qubits
Understanding and suppressing dephasing noise in semiconductor qubits Félix Beaudoin Department of Physics McGill University, Montréal July 2016 A thesis submitted to McGill University in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Physics ©2016 – Félix Beaudoin all rights reserved. Thesis advisor: Professor William A. Coish Félix Beaudoin Understanding and suppressing dephasing noise in semiconductor qubits Abstract Magnetic-field gradients and microwave resonators are promising tools to realize a scalable quantum-computing architecture with spin qubits. Indeed, magnetic-field gradients allow fast se- lective manipulation of distinct qubits through electric-dipole spin resonance and coherent coupling of spin qubits to a microwave resonator. On the other hand, microwave resonators are useful for quantum state transfer and two-qubit gates between distant qubits, and qubit readout. In this thesis, we take a theoretical approach to understand and suppress pure-dephasing mecha- nisms relevant to spin qubits in the presence of the above-mentioned devices, recently introduced to improve scalability. We first focus on dephasing of a spin qubit in the presence of a magnetic-field gradient. We predict that hyperfine coupling of the qubit to an environment of nuclear spins pre- cessing under the influence of a magnetic-field gradient leads to a new qubit dephasing mechanism. We show that in realistic conditions, this new mechanism can dominate over the usual dephasing processes occurring in the absence of a gradient. This result is relevant to spin qubits in GaAs or silicon quantum dots, or at single phosphorus donors in silicon. A magnetic-field gradient may also expose spin qubits to charge noise.