# PQI Public Lectures

### PQI2019 - Dr. Carl J. Williams - *From Platinum to Planck*

**Abstract: **The International System of Units (SI) is the basis for measurements worldwide, and NIST, as the premier National Metrology Institute, has both shaped the development of the SI and led its implementation. On November 16, 2018 the Member States of the Treaty of the Meter voted to revise the International System of Units (SI), changing the world's definition of the kilogram, the ampere, the kelvin and the mole. This decision occurred at the 26th meeting of the General Conference on Weights and Measures (CGPM) in Versailles, France, means that all SI units will now be defined in terms of constants that describe the natural world. This will assure the future stability of the SI and open the opportunity for the use of new technologies, including quantum technologies, to implement the definitions. The actual revision official will come into force on World Metrology Day, 20 May 2019. In the reformed SI, all of the base units will be defined by reference to unchanging constants of nature, finally eliminating any connection between units and special artifacts. This talk will describe why such a radical change was needed; how it is being achieved, in large part driven by work done at NIST; and how new technologies are transforming how we realize and disseminate the SI.

### 2018 - Sir Michael Victor Berry - *Optica Fantastica: Images to Illuminate the Physics of Light*

**Abstract: **A talk based entirely on pictures. Seas sparkle, sunshine generates rainbows, ships make waves. The explanations of these familiar phenomena are as abstract as elsewhere in physics, but pictures are helpful because in light and waves on water we can often see what we are thinking about. There are other optical phenomena that are not immediately perceived (associated with polarization or fine-scale interference, for example), but even with these we can generate pictures to help our understanding. Poets and novelists, as well as painters, have sometimes represented optical phenomena in ways that are surprisingly close to those of physicists.

### PQI2018 - Dr. David D. Awschalom - *Beyond Electronics: Abandoning Perfection for Quantum Technologies*

**Abstract: **Our technological preference for perfection can only lead us so far: as traditional transistor-based electronics rapidly approach the atomic scale, small amounts of disorder begin to have outsized negative effects. Surprisingly, one of the most promising pathways out of this conundrum may emerge from recent efforts to embrace defects to construct 'quantum machines.' Recently, individual defects in diamond and other materials have attracted interest as they possess an electronic spin state that can be employed as a solid state quantum bit at room temperature. The quantum engineering of spins and photons has enabled gigahertz coherent control, nanofabricated spin arrays, nuclear spin quantum memories, and nanoscale imaging for emerging applications in science and technology. We provide an overview of experiments used to generate, manipulate, and interrogate single electron and nuclear spin states on demand.

### PQI2017 - Dr. Chris Monroe - *Building a Quantum Computer, Atom by Atom*

**Abstract: **Laser-cooled and trapped atomic ions are standards for quantum information science, acting as qubits with unsurpassed levels of quantum coherence while also allowing near-perfect measurement. When qubit state-dependent optical forces are applied to a collection of ions, their Coulomb interaction is modulated in a way that allows entanglement operations that form the basis of a quantum computer. Similar forces allow the simulation of quantum magnetic interactions, and recent experiments have implemented tunable long-range interacting spin models with up to 50 trapped ions. Scaling to even larger numbers can be accomplished by coupling trapped ion qubits to optical photons, where entanglement can be formed over remote distances for applications in quantum communication, quantum teleportation, and distributed quantum computation. By employing such a modular and reconfigurable architecture, it should be possible to scale up ion trap quantum networks to useful dimensions, for future quantum applications that are impossible using classical processors.

### PQI2016 - Dr. Michel Devoret - *The Quest for the Robust Quantum Bit*

**Abstract: **Physical systems usually exhibit quantum phenomena, such as state superposition and entanglement, only when they are sufficiently decoupled from a lossy environment. Paradoxically, a specially engineered interaction with the environment can become a resource for the generation and protection of quantum states. Moreover, this notion can be generalized to a manifold of quantum states that consists of all coherent superpositions of multiple stable steady states. In particular, it has now become practically feasible to confine the state of an harmonic oscillator to the quantum manifold spanned by two coherent states of opposite phases. In a recent experiment [1], we have observed a superposition of two such coherent states, also known as a Schrodinger cat state, spontaneously squeeze out of vacuum, before decaying into a classical mixture. The dynamical protection of logical qubits built from Schrodinger cat states is based on an engineered driven-dissipative process in which photon pairs are exchanged rather than single photons. The recent class of experiments in which qubits are encoded using cat states opens a new avenue in quantum information processing with superconducting circuits.

### PQI2015 - Dr. K. Birgitta Whaley - *Quantum Information-Driven Science*

**Abstract: **The growth of quantum information science and technology has spurred advances in study of a broad range of physical, chemical and biological systems, generating novel probes and yielding new insights into fundamental behaviors. Physical and mathematical scientists are increasingly turning to quantum information for fresh insights and tools to study complex systems. I shall summarize this perspective with key examples drawn from diverse physical/chemical/biological settings and then focus on two frontiers of quantum science from my own research, namely study of macroscopic quantum states by controlled quantum feedback and reservoir engineering, and exploration of quantum dynamical contributions to biological processes by multidimensional spectroscopies.

### PQI2014 - Dr. Seigo Tarucha - *Electrical Control of Electron Phase and Correlation in Nanostructures*

**Abstract: **Quantum coherence and entanglement is the fundamental concept of solid state quantum mechanics and quantum information processing as well. This concept has been well developed for photons but not yet for electrons in solid state systems, mainly because the electron coherence is easily disturbed through interactions in the environment including electrons. Recently various techniques have been developed to manipulate, transfer and detect single and correlated electrons in semiconductor nanostructures with preserving the coherence. In this talk I will review some of them: electron phase control and detection using a two-path interferometer consisting of an AB ring with parallel tunnel-coupled quantum wire terminals, electron transfer in a moving quantum dot made by a surface acoustic wave, and finally manipulation and detection of correlated electrons in the spin singlet state using a superconductor as a correlated electron pair source and parallel coupled quantum dots contacted to the superconductor for splitting the electron pairs into two. These techniques may allow various kinds of quantum measurement for electron phase and correlation in solid state systems and also lead to an intriguing field of quantum electron optics.

### PQI2013 - Dr. WIlliam Phillips - *Quantum Information: A Scientific and Technological Revolution for the 21st Century*

**Abstract: **Two of the great scientific and technical revolutions of the 20th century were the discovery of the quantum nature of the submicroscopic world, and the advent of information science and engineering. Both of these have had a profound effect not only on our daily lives but on our worldview. Now, at the beginning of the 21st century, we see a marriage of quantum mechanics and information science in a new revolution: quantum information. Quantum computation and quantum communication are two aspects of this revolution. The first is highly speculative: a new paradigm more different from today’s digital computers than those computers are from the ancient abacus. The second is already a reality, providing information transmission whose security is guaranteed by the laws of physics.