18:00  20:00 
Registration at guest house 4, library 
19:00  21:00 
Welcome reception and dinner at the MPIPKS 
20:00  21:30 
Informal discussions 
Chair morning session: Ines de Vega 

09:15  10:00 
James Wootton
(IBM Research  Zurich)
Benchmarking quantum processors with quantum error correction Almost everything a faulttolerant quantum computer will do will be dedication to a single task: error correction. Performing computations will essentially be a side effect of the error correction process. To determine the performance of such a device, we can therefore focus on how well it implements the detection and correction of errors. In this talk I will present results from a minimal implementation of the repetition code on the 16 qubit Rueschlikon device. I will also propose tests based on the surface code that could be applied to the emerging generation of quantum processors. 
10:00  10:30 
Coffee break 
10:30  11:15 
Howard Carmichael
(University of Auckland)
Monitored quantum jumps: the view from quantum trajectory theory Quantum jumps are emblematic of all things quantum. Certainly that is so in the popular mind. And more than merely an echo from the past, the term “quantum jump” still holds a prominent position within the lexicon of modern physics today. What, however, is the character of the jump on close inspection? Is it discontinuous and discrete, as in Bohr’s original conception? Or is it some form of continuous Schrödinger evolution that might be monitored and reconstructed, even interrupted and turned around? I consider the jumps of single trapped ions observed in the mid1980s [1], where the view from quantum trajectory theory favours the latter option. I present that view and support it with experimental results [2], which recover the continuous and deterministic path of quantum jumps in a superconducting circuit from conditional quantum state tomography. [1] W. Nagourney et al., Phys. Rev. Lett. 56, 2797 (1986); T. Sauter et al., Phys. Rev. Lett. 57, 1696 (1986); J. C. Bergquist et al., Phys. Rev. Lett. 57, 1699 (1986). [2] Z. K. Minev, S. O. Mundhada, S. Shankar, P. Rheinhold, R. GutiérrezJáuregui, R. J. Schoelkopf, M. Mirrahimi, H. J. Carmichael, and M. H. Devoret, arXiv:1803.00545 (2018). 
11:15  12:00 
Lorenza Viola
(Dartmouth College)
Qubit sensors in correlated quantum noise environments: from noisy quantum metrology to quantum noise spectroscopy Qubit systems offer unique opportunities for sensing and estimation. On the one hand, the use of entangled qubit states can yield measurement precision that exceeds the optimal bounds achievable classically. On the other hand, the exquisite sensitivity of qubits to their surrounding environment makes them natural spectrometers of their own noise. In this talk, I will present recent results on both parameter estimation and spectral estimation by qubit sensors in realistic correlated noise environments. I will first consider the paradigmatic setting of frequency estimation by Ramsey interferometry and show how spatiotemporally correlated quantum noise, characterized by frequencyasymmetric spectra, can introduce additional sources of uncertainty due to uncontrolled entanglement of the qubit sensors mediated by the bath. In particular, I will discuss how this analysis is directly relevant to amplitude sensing experiments with trapped ion crystals. I will then highlight some of our efforts toward developing control methods for quantum noise spectroscopy. In particular, I will describe how protocols inspired by both dynamical decoupling and spinlocking relaxometry may be used to characterize nonGaussian noise sources as well as noise correlations, and outline experimental validation using superconducting qubit devices. 
12:00  13:00 
Lunch break 
13:00  14:00 
Discussions 
Chair afternoon session: Thomas Barthel 

14:00  14:30 
Luis Pedro GarcíaPintos
(University of Massachusetts Boston)
Spontaneous symmetry breaking induced by quantum monitoring The information acquired during the monitoring of a quantum system provides a state description that can differ greatly from the description given by agents ignorant of the outcomes. While the lack of information in the latter results in a mixed density matrix following open system dynamics, the measurement backaction in the former case provides a more accurate description. I discuss the consequences of such measurement backaction to two problems in quantum theory, the derivation of limits to the speed of evolution, and the process of spontaneous symmetry breaking, focusing on the different descriptions that agents provide of a given system. 
14:30  15:00 
Andrea Smirne
(Ulm University)
Nonperturbative method for nonMarkovian quantum dynamics We characterize the conditions which allow us to describe the general, nonMarkovian dynamics of an open quantum system by means of a simpler model, consisting in an enlarged set of degrees of freedom undergoing a Markovian (Lindbladian) dynamics. After presenting the equivalence theorem between the two systems, we show how to exploit it to build up in a systematic and certied way auxiliary models, which can be treated efficiently by means of existing numerical techniques. 
15:00  15:30 
Mark Mitchison
(Trinity College Dublin)
Quantum thermodynamics with quasiperiodic systems Quasiperiodic systems in one dimension display extremely rich transport properties, including a localisation transition with a mobility edge and anomalous subdiffusive behaviour in certain regimes. Here we exploit the mobility edge and unusual band structure of a quasiperiodic system to create an energy filter for energy and particle transport. We show how this can be used to construct a highly efficient heat engine that extracts electrochemical power from a temperature gradient. This points to the significant potential of quasiperiodic systems for quantum thermodynamics. 
15:30  16:00 
Durga B Rao Dasari
(Max Planck Institute for Solid State Research & University of Stuttgart)
Nonclassical measurement statistics induced by a coherent spin environment Quantum mechanics allows us to postselect events that cannot be observed classically. Even though these events are rare we cannot create a classical setup that allows us to observe such an effect. Strong projective measurements that lead to the wavefunction collapse of the measured system also could perturb its coupled environment. While such control has been mostly used for quantum state preparation of small nuclear spin ensembles and in cavity QED experiments, inducing/transducing quantum mechanical properties onto the measurement statistics itself has not been achieved. We experimentally and theoretically demonstrate this fundamental effect in a central spin model, where the measurement (backto)back action of the measured central spin and its coupled environment onto each other lead to nonclassical (Quantum Random Walk like) measurement statistics of the central spin. Using Nitrogen Vacancy centers in diamond as the central spin, and its projective singleshot readout at low temperatures, we show how the coherent nuclearspin environment to which it is coupled allows its measurement statistics display nonclassical features. The longlife time of the spin environment correlating subsequent measurements also leads to bathengineering i.e., a modified bath spectrum, resulting in an enhanced coherence time ($T_2^*$) of the central spin. The observed nonclassical statistics and bath purification could be important for quantumness certification protocols and for quantum state engineering. 
16:00  16:30 
Coffee break 
Chair late afternoon session: Pieter W. Claeys 

16:30  17:00 
Ali Tayefeh Rezakhani
(Sharif University of Technology Tehran)
Detailed balance and fluctuation relations in quantum thermodynamics Quantum detailed balance conditions and quantum fluctuation relations are two important concepts in the dynamics of open quantum systems; both concern how such systems behave when they thermalize because of interaction with an environment. I show that for thermalizing quantum dynamics the quantum detailed balance conditions yield validity of a quantum fluctuation relation (where only forwardtime dynamics is considered). This implies that to have such a quantum fluctuation relation (which in turn enables a precise formulation of the second law of thermodynamics for quantum systems) it suffices to fulfill the quantum detailed balance conditions. I, however, argue that the converse is not necessarily true; there exit cases of thermalizing dynamics which feature the quantum fluctuation relation without satisfying detailed balance. 
17:00  17:30 
Babak Seradjeh
(Indiana University Bloomington)
Higherorder Floquet topological phases with corner and bulk bound states We report the theoretical discovery and characterization of higherorder Floquet topological phases dynamically generated in a periodically driven system with mirror symmetries. We demonstrate numerically and analytically that these phases support lowerdimensional Floquet bound states, such as corner Floquet bound states at the intersection of edges of a twodimensional system, protected by the nonequilibrium higherorder topology induced by the periodic drive. We characterize higherorder Floquet topologies of the bulk Floquet Hamiltonian using mirrorgraded Floquet topological invariants. This allows for the characterization of a new class of higherorder ``anomalous'' Floquet topological phase, where the corners of the open system host Floquet bound states with the same as well as with double the period of the drive. Moreover, we show that bulk vortex structures can be dynamically generated by a drive that is spatially inhomogeneous. We show these bulk vortices can host multiple Floquet bound states. This ``stirring drive protocol'' leverages a connection between higherorder topologies and previously studied fractionally charged, bulk topological defects. Our work establishes Floquet engineering of higherorder topological phases and bulk defects beyond equilibrium classification and offers a versatile tool for dynamical generation and control of topologically protected Floquet corner and bulk bound states. 
17:30  18:00 
Alvaro Alhambra
(Perimeter Institute for Theoretical Physics)
Dynamics of twopoint correlation functions in quantum manybody systems We give rigorous analytical results about the behavior of twopoint correlation functions in quantum many body systems undergoing unitary dynamics (also known as dynamical response functions or Green’s functions). These appear in the characterization of wide range of statistical and nonequilibrium phenomena, including quantum transport, fluctuationdissipation theorems, linear response theory or scattering experiments. First, using recent results from large deviation theory, we are able to show that in a large class of models the correlation functions factorize at late times, proving that dissipation emerges out of the unitary dynamics of the system. We also show that the fluctuations around this latetime value are bounded by the “effective dimension”, which generally decays exponentially with system size. This result connects the behavior of correlation functions to the physics of equilibration of quenched systems. Moreover, for autocorrelation functions such as (including the symmetric and antisymmetric versions) we provide an upper bound on the timescale at which they reach the “dissipated” late time value. Remarkably, this turns out to be related to local expectation values only, and it doesn’t increase with system size. We give numerical examples that illustrate how this upper bound is in fact a good estimate, and we argue this timescale can be understood in terms of an emergent fluctuationdissipation theorem. Our study extends to larger classes of two point functions. In particular, we also show that the Kubo correlation function that controls the linear response theory evolves under a similar timescale. 
18:00  19:00 
Discussions 
19:00  20:00 
Dinner 
20:00  21:00 
Poster session II (focus on even poster numbers) 