CQT Talk by Bhanu Pratap Das, Tokyo Institute of Technology

Title: Role of AMO Theory in Probing the Standard Model of Particle Physics via the Electron and Nuclear Electric Dipole Moments
Date/Time: 19-Sep, 03:30PM
Venue: CQT Level 3 Seminar Room, S15-03-15

Abstract: The electron and nuclear electric dipole moments (EDMs) which could exist due to time-reversal (T) and parity (P) violations are two important probes of new physics beyond the Standard Model (BSM). Heavy polar molecules are currently the leading candidates for the searches for the electron EDM (eEDM). The best limits for this quantity come from ThO, HfF+ and YbF. The first part of my talk will deal with the analysis of the large T and P violating effect related to the eEDM in mercury halides using relativistic many-body theory. These molecules are promising candidates to search for the eEDM. The T and P violating nuclear Schiff moment (NSM) can provide important insights into BSM physics particularly those predicted by a number of supersymmetric models. In the second part of my talk, I shall use a specific kind of relativistic many-body theory to present results for the ratio of the EDM of mercury atom to its NSM. Combining the most accurate of these results with the latest measurement of the EDM of mercury, I shall present new results for hadronic T violation involving quarks.

CQT Colloquium by Timothy C. Ralph, Centre for Quantum Computation & Communication Technology, The University of Queensland

Title: Quantum Entanglement: Gaussian and Macroscopic
Date/Time: 18-Oct, 04:00PM
Venue: CQT Level 3 Seminar Room, S15-03-15

Abstract: In the first half of this talk I will discuss the quantification of entanglement in Gaussian systems and how this relates to channel simulation and error correction. We conclude that entanglement of formation is a more faithful measure of entanglement in Gaussian systems than negativity, both qualitatively and quantitatively, and illustrate this with examples. In the second half of this talk I will discuss the macroscopicity problem in quantum mechanics. If quantum theory is universal we would expect to be able to observe quantum effects such as superpositions on a macroscopic scale. The current inability to observe such effects is commonly attributed to decoherence, leading to a so-called “macro-scale” beyond which physical systems can be analysed without any reference to the quantum formalism. We challenge this view by showing that, with the assistance of a second system, a macroscopic system can be proved to be entangled even after arbitrary decoherence. We show this by introducing a modified Wigner’s friend gedankenexperiment where the observer is not assumed to preserve quantum coherence.

CQT Lecture series by Bhanu P. Das, Tokyo Institute of Technology

Title: Relativistic Many-Body Theory of Atoms (Lecture 4)
Date/Time: 20-Sep, 03:00PM
Venue: CQT Level 3 Seminar Room, S15-03-15

Abstract: Applications of Relativistic Coupled Cluster Method to Hyperfine Interactions in Atoms, Electric Dipole Moments of Atoms due to Parity and Time Reversal Violations and Electric Quadrupole Moments of Atoms

CQT Talk by Guillermo Romero, The University of Santiago, Chile

Title: Nucleation of superfluid-light domains in a quenched dynamics
Date/Time: 17-Oct, 11:00AM
Venue: CQT Level 3 Seminar Room, S15-03-15

Abstract: Strong correlation effects emerge from light-matter interactions in coupled resonator arrays, such as the Mott-insulator to superfluid phase transition of atom-photon excitations. We demonstrate that the quenched dynamics of a finite-sized complex array of coupled resonators induces a first-order like phase transition. The latter is accompanied by domain nucleation that can be used to manipulate the photonic transport properties of the simulated superfluid phase; this in turn leads to an empirical scaling law. This universal behavior emerges from the light-matter interaction and the topology of the array. The validity of our results over a wide range of complex architectures might lead to a promising device for use in scaled quantum simulations.

CQT Industry Talk by Ben Miles and Andy Collins, QTEC, UK

Title: Developing Leaders in Quantum Technologies: The QTEC Fellowship Program
Date/Time: 02-Oct, 04:00PM
Venue: CQT Level 3 Seminar Room, S15-03-15

Abstract: The Quantum Technology Enterprise Centre (QTEC) is a world-first incubator for quantum-based technology innovators. Its vision is to educate and create the quantum entrepreneurs of the future who will be the foundation, pillars, and growth of the UK’s and the Global Quantum Industry. Its mission is to develop the thought leaders and entrepreneurs who will take quantum technologies out of the lab and into the real world. QTEC is a collaboration between the University of Bristol and The Bettany Centre for Entrepreneurship at Cranfield University. We are part of the £270M UK National Quantum Technologies Programme which has a mission to support the translation of revolutionary quantum technology from the lab into the commercial market. Our aim is to produce the pioneers and businesses that will make the UK a global leader in the sectors where the emergence of quantum engineering will have a transformative impact.

CQT Talk by Srijita Kundu, CQT

Title: Shadow Tomography of Quantum States
Date/Time: 21-Sep, 03:00PM
Venue: CQT Level 3 Seminar Room, S15-03-15

Abstract: In this journal club session I will discuss the paper 'Shadow Tomography of Quantum States' by Aaronson. The abstract of the original paper is as follows.

• We introduce the problem of shadow tomography: given an unknown -dimensional mixed quantum state , as well as two-outcome measurements , estimate the probability that accepts , to within additive error , for each of the measurements. Surprisingly, we give a procedure that solves the problem by measuring only copies. This means, for example, that we can learn the behavior of an arbitrary -qubit state, on all accepting/rejecting circuits of some fixed polynomial size, by measuring only copies of the state. This resolves an open problem of the author, which arose from his work on private-key quantum money schemes, but which also has applications to quantum copy-protected software, quantum advice, and quantum one-way communication. Recently, building on this work, Brandao et al have given a different approach to shadow tomography using semidefinite programming, which achieves savings in computation time.

CQT Talk by Alexandre Roulet, University of Basel

Title: Synchronizing the Smallest Possible System
Date/Time: 19-Sep, 11:00AM
Venue: CQT Level 3 Seminar Room, S15-03-15

Abstract: Synchronization is ubiquitous in our everyday life. It successfully describes complex classical systems such as electronic and biological networks, and there is a growing interest in understanding how it applies to quantum systems. However, when moving from a classical to a quantum framework, one is inevitably confronted with the exponential growth of the state space as opposed to the linear classical scaling, which limits the tractable size of a network of quantum oscillators. In this work [1], we approach this issue by addressing the fundamental question of the minimal dimension for a quantum system to be synchronized. We first show that the standard paradigm of synchronization does not apply to a two-level system due to the lack of a limit cycle. Surprisingly, we then find that a single spin 1 – a system with no classical analogue – can be phase-locked to a weak external signal of similar frequency and exhibits all the features of the theory of synchronization. Our results rely on a proposed phase portrait applicable to spin systems, in which we can identify the phase variable that lies at the core of the formalism. We discuss the relation between quantum synchronization and entanglement in a subsequent work [2]. [1] A.Roulet and C.Bruder, PRL 121,053601 (2018) [2] A.Roulet and C.Bruder, PRL 121,063601 (2018)