In this talk, we review the connection between thermalization in isolated many-body quantum systems and the emergence of quantum chaos. This relationship is explored to address the timescales for isolated many-body quantum systems to reach thermal equilibrium after a dynamical quench, which remains an important open question. We examine how the equilibration process depends on the models,...
Quantum technologies play a crucial role in both scientific and technological advancement, leveraging the unique properties of quantum mechanics - such as superposition and entanglement - to enhance the performance of classical systems and enable new device functionalities. Light-based quantum technologies utilize photons as fundamental carriers of information, taking advantage of their long...
Superconducting nanowire single photon detectors (SNSPDs) are advanced devices renowned for their high system efficiency up to 98% at infrared wavelengths, low dark count rate less than 0.02 cps, and fast count rate, making them ideal for single photon detection applications such as quantum communication, photonic quantum computing, imaging, and LIDAR. Today, I will share the advanced SNSPD...
High-dimensional quantum key distribution rates for multiple measurement bases Quantum key distribution (QKD) protocols take at least two advantages from high-dimensional (HD) systems: the secret key rate scaling as the dimension and the opportunity of exploiting more than two mutually-
unbiased bases (MUBs). Indeed, if the dimension d of the system is a prime power, then d + 1 MUBs exist....
In this presentation I will talk about an application of quantum computing to compose artworks. The main idea of this project is to revisit three paintings of different styles and historical periods: “Narciso”, by Michelangelo Merisi (Caravaggio), “Les fils de l’homme”, by René Magritte and “192 Farben”, by Gerard Richter. We utilize the output of a quantum computation to change the...
We review some recent results on developing efficient tree tensor network algorithms and their application to quantum simulation benchmarking and theoretical interpretations. In particular, we present results on two- and three-dimensional systems in and out of equilibrium and on the computation of entanglement of formation in critical quantum many-body systems at finite temperature. Finally,...
Quantum simulations are essential for exploring open quantum systems. However, balancing ease of use with high computational performance remains a challenging task. In this talk, I present QuantumToolbox.jl, an open-source Julia package for simulating open quantum dynamics. Designed with a syntax familiar to users of QuTiP (Quantum Toolbox in Python), QuantumToolbox.jl leverages Julia’s...
A universal quantum computer has to execute a long series of high-fidelity gates to be useful, which is very difficult to achieve experimentally. However, universal computing is only one approach to computation. There are other forms which sacrifice universality for fewer requirements on the physical system, such as analog simulation, annealing or variational approaches. This talk is about...
Quantum state designs enable efficient sampling of random quantum states, with applications ranging from circuit design to black hole physics. While symmetries are known to reduce randomness, their role in generating state designs remains unclear. The projected ensemble framework [2, 3], which uses local projective measurements and many-body quantum chaos, has recently been introduced to...
In physics, symmetries are ubiquitous. Quantum simulation of symmetry-constrained systems represent an outstanding challenge in the rapidly evolving field of quantum technology and information. A key prerequisite is the protection of the symmetry sector we want to study against errors that, if unchecked, would lead to unwanted symmetry-breaking results. In this framework, post-selection is one...
Epitaxial semiconductor-superconductor hybrid materials provide a novel highly-tunable platform to study exotic emergent quantum phenomena, taking advantage of gate-controlled density, ballistic transport, and non-sinusoidal current-phase relations.
In my talk, I will introduce the hybrid Josephson rhombus, a highly tunable superconducting circuit element containing four...
Recent experiments in hybrid semiconductor-superconductor devices demonstrated the possibility of realizing the so called "Poor man's Majorana modes" (PMMs). These are zero-energy modes that fulfill most of the properties of standard Majorana modes in topological superconductors, despite not being topologically protected. PMMs are indeed realized in fine-tuned devices composed by quantum dots...
I will present a mapping that transforms the kinetically constrained PXP model into a constrained XX model with non-local constraints. The constraint can be tuned to interpolate between the free fermionic XX model at one end and the PXP model at the other. This transformation reveals additional conservation laws that help explain some of the unusual properties of the model. Finally, I will...
Variational quantum algorithms are particularly promising early applications of quantum computers since they are comparatively noise tolerant and aim to achieve a quantum advantage with only a few hundred qubits. They are applicable to a wide range of optimization problems arising throughout the natural sciences and industry. To demonstrate the possibilities for the aeroscience community, we...
Interactions can play a determinant role in low dimensions for topological and chiral states of matter by giving rise to interesting emergent phenomena such as quasiparticle fractionalization and quantum phase transitions. Recent experimental evidence from Floquet engineered ultracold atomic systems [1], have provided a starting point for observing correlated vortex structures of the Laughlin...
Quantum many-body problems, such as the study of nuclear structure, are difficult to treat with classical computers due to exponential complexity. One way to overcome this limitation would be to use quantum computers, which allow to reduce computational cost. In this context, it is important to test quantum algorithms on simple, yet nontrivial models, with the goal of assessing their...
The quantum Ising model on a square lattice exhibits an emergent dynamical constraint: in the ordered phase, the dynamics approximately conserve the total length of the domain walls. We numerically investigate the dynamics in the crossover from the constrained to the diffusive regime on lattices of up to 16×16 spins. The dynamical constraint, and the subsequent fragmentation of the Hilbert...
An optomechanical microcavity can considerably enhance the interaction between light and mechanical motion by confining light to a subwavelength volume. However, this comes at the cost of an increased optical loss rate. A pathway to reduce optical losses is to use a strongly frequency-dependent mirror, such as a photonic crystal mirror.
In this talk, I will present the quantum-coupled-mode...
Color centers have become a hot topic in recent times for their potential applications in quantum technologies particularly in the context of realizing quantum networks. Employing a scheme that relies on the coupling between single photons and atom-like transitions among spin states in a diamond colour center, it is possible to exploit both the strong coherence properties of photons and the...
Janas is a startup that uses quantum computing technologies and techniques to solve today's industrial problems. In the NISQ settings, we think that only a hybrid approach with the right mix of conventional high performance computing (the specialty of our parent company eXact lab), machine learning and quantum processing can provide an edge in the near term. We further claim that quantum...
For the last five years, quantum computing has been in the era colloquially known as 'NISQ' - where computation is limited by error rates instead of qubit count. The next steps on quantum computing roadmaps push us into the early-fault tolerant era. Here, limited amounts of error correction will be available, but achieving beyond-classical quantum computation will require robust algorithm...
Since their initial proposal, materials with a negative refractive index, also dubbed as left-handed, have attracted significant interest because of their unusual electromagnetic properties and promising technological applications. Recently, they have gained renewed attention in the field of circuit quantum electrodynamics as potential platforms for achieving near-quantum-limited parametric...
Analog quantum computing is emerging as a powerful approach for addressing computationally intractable problems in quantum many-body physics. Classical computers struggle to simulate these systems due to the exponential growth in computational resources required as system size increases. Unlike digital quantum computers, which rely on discrete qubits and gate-based operations, analog quantum...
In this work, we compare the quantum simulation of a pionless effective field theory using the first and second quantization frameworks, as well as evaluate the performance of various algorithms within the first quantization framework. We demonstrate that using the first quantization formalism can yield an exponential advantage over second quantization as the lattice size increases. However,...
Quantum phase estimation (QPE) is a flagship algorithm for quantum simulation on fault-tolerant quantum computers. However, recent resource stimates[1] suggest that surpassing classical simulation techniques requires millions of gates and hundreds of logical qubits. Consequently, significant effort is being devoted to developing QPE-like algorithms that could demonstrate practical quantum...
We introduce a hybrid classical–quantum algorithm designed to efficiently compute molecular spectra. Our approach combines classical methods with sample‐based quantum diagonalization, using snapshots of the quantum system’s evolution at selected times we construct a tailored subspace. By integrating these classical techniques with a post-evolution sampling strategy, we effectively capture the...
A method is developed to solve the few-body problem for systems of quantum particles in the bound states. In the framework of the variational method in the Gaussian representation, the structure characteristics of light nuclei 6Li, 6He, 10Be, 10C, 14C, 14N, 14O are studied within three-, four-, and five-cluster models (α-clusters plus two extra nucleons). Specific properties of the charge...
In this talk I will discuss a selection of recent and current QKD activities in Denmark including research results and field demonstrations as well as the status and plans for the Danish Quantum Communication Infrastructure - QCI.DK
Fusion-based quantum computing (FBQC) is a promising model for realizing photonic quantum computers. Compared to measurement-based quantum computing (MBQC), FBQC does not require the generation of a full photonic cluster state prior to measurements. Instead, the cluster state is generated and simultaneously measured by fusions between smaller entangled states. The current approach to generate...
The introduction of high kinetic platforms in circuit QED allow for realization of coupled cavity array with low disorder, small footprint and large inter-site couplings [1]. This enables the study of challenging regimes of light-matter interaction within the paradigm of waveguide QED [2] e.g., giant qubits coupled non-locally to the waveguide. In this work, we conduct an experiment using a...
Variational quantum algorithms, such as the variational quantum eigensolver (VQE), have a very high cost due to the large number of measurement outcomes that must be acquired from the quantum device during training. This is due in large part to the use of the parameter shift rule for estimating the gradient at each step, which requires two circuit evaluations per parameter. It was recently...
Janas is a startup that uses quantum computing technologies and techniques to solve today's industrial problems. In the NISQ settings, we think that only a hybrid approach with the right mix of conventional high performance computing (the specialty of our parent company eXact lab), machine learning and quantum processing can provide an edge in the near term. We further claim that quantum...
Quantum simulations are essential for exploring open quantum systems. However, balancing ease of use with high computational performance remains a challenging task. In this talk, I present QuantumToolbox.jl, an open-source Julia package for simulating open quantum dynamics. Designed with a syntax familiar to users of QuTiP (Quantum Toolbox in Python), QuantumToolbox.jl leverages Julia’s...
Quantum state designs enable efficient sampling of random quantum states, with applications ranging from circuit design to black hole physics. While symmetries are known to reduce randomness, their role in generating state designs remains unclear. The projected ensemble framework [2, 3], which uses local projective measurements and many-body quantum chaos, has recently been introduced to...