Open Questions in Quantum Physics: Information, Computation and Foundations

14 Nov 2019, 09:00 → 15 Nov 2019, 18:00 Europe/Amsterdam

Erasmus High Bay (ESTEC)

Alexandre Feller (ESA), Benjamin Roussel (ESA), Leopold Summerer (ESA)

Quantum theory is, with general relativity, the major theoretical achievement of modern physics. It has nowadays spread into every area of science and a huge amount of research are dedicated to understand and develop technologies using the fundamental features of quantum theory. Research in quantum information, quantum communication and computation  have led to many breakthrough in technological developments but also to our fundamental understanding of the physical world. And the promises, like developing a quantum computer, open up many new perspectives for progresses in technologies and science.

Space research has been and will be greatly influenced by the new developments of quantum theory. On the technological side, communication protocols, which have been transformed by the use of quantum resources, or the use of enhanced sensors using the fundamental properties of quantum systems will greatly improve the scientific potential of space missions. Moreover, the new possibilities offered by quantum computation and simulation will enable new technological developments like the manufacturing of materials with specific physical properties from first principles. This will naturally have consequences on the way space missions are designed. From a science perspective, space remains a vast laboratory to test quantum theory on scales which are not accessible on Earth-based experiments. For instance, space is the perfect laboratory to test the interplay between gravity and quantum theory, from the simple experiments testing the coherence properties of massive objects (QPPF CDF Study) to observing large astrophysical events where gravity and quantum theory should both play a fundamental role (early universe and black hole physics).

This conference purpose is to present in a synthetic way the progresses made in the fields of quantum information,quantum computation and quantum foundations and to put them in perspective for future space applications.

Invited speakers

 - Immanuel Bloch (Max-Planck-Institut für Quantenoptik)
 - Daniel Estève (SPEC, Université Paris-Saclay, CEA-Saclay)
 - Franck Laloë (LKB, École Normale Supérieure)
 - Günther Hasinger (European Space Agency)
 - Jean-Michel Raimond (LKB, Collège de France, ENS, CNRS and Sorbonne Université)
 - Christophe Salomon (LKB, École Normale Supérieure)
 - Augusto Smerzi (QSTAR, INO-CNR and LENS)
 - Rupert Ursin (Institute for Quantum Optics and Quantum Information)
 - Ronald de Wolf (QuSoft, CWI and University of Amsterdam)

programme.pdf

Thursday, 14 November

09:00 → 09:30 Coffee and registration

09:30 → 09:40 Opening

09:40 → 10:55 Exploring and exploiting the quantum with Rydberg atoms

The exploration of the puzzling features of the quantum, like state superpositions, entanglement or measurement processes is a thriving experimental field. It is driven by fascinating applications of the quantum, like quantum metrology, quantum information processing or quantum simulation.

Rydberg atoms, long-lived and extremely strongly coupled to external fields, are ideal tools to explore these basic quantum features. We will review a few explorations of the quantum performed at Collège de France using these remarkable states.

The strong interaction of circular Rydberg states with microwave fields in high quality superconducting cavities lead to illustrations of the quantum measurement postulates, or to the generation of field states reminiscent of the famous Schrödinger cat. Coherent manipulations in the complex Rydberg manifold lead to the observation of quantum Zeno dynamics and to the realization of ultra-sensitive electric and magnetic field measurements. Finally, I will present a quantum simulator project emulating spin chains with laser-trapped circular Rydberg atoms.

Speaker: Jean-Michel Raimond

10:55 → 11:15 Coffee

11:15 → 12:30 Hyper and microgravity experiment using entangled photons

Speaker: Rupert Ursin

12:30 → 13:00 The ESA Voyage2050 Strategic Plan

Speaker: Günther Hasinger (European Space Agency)

13:00 → 14:00 Lunch

14:00 → 15:15 Quantum Algorithms

This talk will give an introduction to quantum algorithms, which are the core of the "software" of quantum computers. We will go into algorithms relevant for cryptography (such as Shor's factoring algorithm), for optimization tasks (such as Grover search and the HHL algorithm), and for simulation of physical systems. We will also briefly look at known limitations of quantum computers.

Speaker: Ronald de Wolf

15:15 → 16:30 Witnessing entanglement with statistical speeds: from fundamental physics to quantum technologies

We discuss the profound relation provided by quantum mechanics between the possibility to statistically distinguish quantum states and multipartite entanglement. This relation provides a general framework to investigate different technologies, including quantum precision measurements (interferometric phase estimations and metrology) as well as fundamental problems like the nature of the resources exploited in the Grover search algorithm and the violation of the CHSH-Bell inequality.

Speaker: Augusto Smerzi

16:30 → 16:50 Coffee

16:50 → 18:05 Various interpretations of quantum mechanics, relations with gravity

In most fields of physics (atomic and molecular physics, condensed matter, quantum electrodynamics, etc.), the way quantum mechanics should be applied in practice is perfectly consensual. Nevertheless, how it should be interpreted and really understood is less clear; new articles are still constantly published to propose various interpretations, and controversies may even take place. Another difficulty is the connection with gravity, which is for instance necessary in quantum cosmogenesis. The talk will give an overview of the major families of interpretations of quantum mechanics and  their specificities. It will in particular discuss interpretations relating quantum collapse to the effects of gravity (Diosi, Penrose, Bohmian collapse).

Speaker: Franck Laloë

Friday, 15 November

09:00 → 09:15 Coffee

09:15 → 10:30 Large Scale Quantum Simulations using Ultracold Atoms

More than 30 years ago, Richard Feynman outlined his vision of a quantum simulator for carrying out complex calculations on physical problems. Today, his dream is a reality in laboratories around the world. This has become possible by using complex experimental setups of thousands of optical elements, which allow atoms to be cooled to nanokelvin temperatures, where they almost come to rest. In my talk I will discuss the different platforms for quantum simulation using neutral atoms and ions and discuss selected application highlights ranging from material science to optimisation schemes. I will discuss the status of the field and give an outlook on future scalability of the different underlying systems.

Speaker: Immanuel Bloch

10:30 → 10:50 Coffee

10:50 → 12:05 Quantum microwave optics in simple Josephson junction circuits

A Josephson junction in series with an impedance and voltage biased below the gap provides a simple quantum electrodynamics system in which the coupling constant between charge transfer across the junction and each mode of the impedance is determined by the ratio between the mode impedance and the relevant resistance quantum. Circuit engineering allows to implement interesting situations beyond reach of quantum optics in atomic physics, and noticeably to reach large values of the coupling constant.

In the simplest case of a single mode resonator, the transfer of a single Cooper pair only occurs when its energy 2eV can be transformed in 1,2,...,n excitations in the resonator. This inelastic tunneling phenomenon is the essence of Dynamical Coulomb Blockade. In the strong coupling regime, a single Cooper pair transfer can be associated to the emission of a few photons in the external circuit. The presence of a single excitation in the resonator can even block the creation of a second one, which then forces the resonator to emit a single photon in the external circuit before another Cooper pair can pass and re-excite it. This phenomenon provides a very simple single photon source.

In a two resonator circuit with different frequencies, the transfer of a single Cooper pair can simultaneously excite a single excitation in each resonator. The photons leaking out of the two resonators in the measurement lines are then entangled, which was probed. In the particular case of two resonators respectively with a high (low) quality factor, the stabilization of a single excitation Fock state in the high Q resonator could furthermore be achieved.

Applications are sought for these non-classical sources of radiation in the microwave domain that could be extended up to the THz frequency range, a quite unexplored domain of the electromagnetic radiation spectrum.

Speaker: Daniel Estève

12:05 → 13:20 Precision Quantum Measurements on Earth and in Space

Speaker: Christophe Salomon

13:20 → 13:30 Closure