A useful quantum computer will require quantum-error-correction, which implies a huge increase in resources over systems in laboratories today. In this context, I will describe work towards scaling up trapped-ion quantum computing, including the use of integrated optics, ion shuttling, and attempts to meet the challenges of calibrating and stabilizing larger scale devices. These core elements...
Future quantum networks offer a route to quantum-secure communication, distributed quantum computing, and quantum-enhanced sensing. The applications of a given network will depend on the capabilities available at its nodes, which may be as simple as quantum-state generation and measurement or as advanced as universal quantum computing. Here, we focus on quantum nodes based on trapped ions,...
Quantum simulation enables studying the dynamics of quantum many-body systems in regimes which are inaccessible to numerical methods. With universal digital quantum simulators, time evolution generated by a large class of Hamiltonians can be simulated by approximating the unitary time-evolution operator by a sequence of quantum gates. However, this "Trotterization" introduces an intrinsic...
In quantum systems composed of at least two subsystems, entanglement induces correlations between the properties of the subsystems that cannot be reproduced in classical physics. These strong correlations are used as a resource for many innovative applications of Quantum Physics, such as quantum computation and quantum communication.
One operationally meaningful way to characterise this...
Quantum computers allow for a higher level of security in information exchange than their classical counterpart. As an example, by using the so-called blind quantum computing protocols, a client can delegate a complex quantum computation to a server in a completely secure way, without any leaks of information on the input, the output or the computation algorithm. In this work, we realize a...
Quantum communication is one of the most advanced areas of quantum science and technology. It spans commercial devices and systems already deployed to future concepts of a quantum internet. We introduce some of the underlying concepts and targeted applications in this rapidly expanding and advancing field. We start with the simple concept of quantum random number generation and their...
Quantum memories are an essential ingredient for quantum repeaters. Further, through synchronization they can facilitate the generation of multiphoton states. This enables scaling optical quantum information processing experiments into a regime beyond the realm of classical simulation. We implemented a broadband optical quantum memory with on-demand storage and retrieval in hot Rb vapor....
Quantum memories are key devices for future quantum networks. The atomic frequency comb (AFC) scheme in rare-earth doped crystals provides solid-state memories with many appealing features, such as high efficiency, multimode capacity and long storage times. The previous record storage time achieved in an AFC memory was around 1 ms, in a Europium-doped Y2SiO5 crystal at zero applied magnetic...
Mechanical oscillators have a rich history and role in precision science, ranging from the atomic force microscope, gravitational wave detection to technology such as filters in cell phone or quartz oscillators. The dissipation of the mechanical oscillator plays a key role in setting the thermal decoherence rate, limiting e.g. the ability to observe radiation pressure quantum effects, or...
Quantum simulations open the path for understanding complex quantum matter. Among the large variety of possible approaches, ultracold quantum gases offer a skilful realization of models in condensed matter physics from the weakly to the strongly correlated regime. The key benefits lie on in the ability to reach a high degree of isolation and state control, to change the system’s...
A Bose-Einstein Condensate (BEC) inside an optical resonator can undergo a phase transition to a self-organised state when illuminated with a red-detuned pump beam.
In our recent experiment, we explore the blue-detuned case. We observe that self-organisation is still possible despite the atoms being expelled from the light fields. Moreover, the repulsive lattice modifies the inter-band...
Controlling the internal state of a particle in an ultracold atom experiment is important for studying spinor phases and to simulate spin physics. This control can be implemented using light fields that couples differently to the internal states. This was successfully used in several experiments, although the experiment time is usually constrained by the heating induced by the laser beams....
Superconducting circuits are a prime contender for realizing universal quantum computation in fault-tolerant processors and for solving noisy intermediate-scale quantum (NISQ) problems with non-error-corrected ones. Superconducting circuits also play an important role in state of the art quantum optics experiments and provide interfaces in hybrid systems when combined with semiconductor...
In order to perform simulations of quantum systems on current quantum processors, quantum algorithms with short circuit depth have to be designed. Here, we experimentally demonstrate that exchange-type gates, tunable in amplitude and phase, are ideally suited for calculations in quantum chemistry [1]. We optimize and characterize these exchange-type gates, which yield an average gate fidelity...
Since the very first experiments, superconducting circuits are suffering from coupling to environmental noise, destroying quantum coherence and degrading performance. In state-of-the-art experiments, it is found that the relaxation time of superconducting qubits fluctuates as a function of time. We present measurements of such fluctuations in 2D and 3D-transmon circuits and develop a...
We will present recent experimental progress with micro-machined silicon nanomechanical systems. The interplay between parametric driving, interference and dissipation in a multi-mode cavity electro-optomechanical system can either be used to break time reversal symmetry and act as a compact on-chip microwave circulator [1], to realize bidirectional microwave to telecom conversion, or to...
Quantum illumination is a quantum sensing technique in which quantum correlation is used to improve the detection of a low-reflectivity object that is immersed in a bright thermal background. Here, using a superconducting circuit platform we experimentally implement quantum illumination at microwave frequencies. We use a Josephson parametric converter to generate stationary entanglement...
Hole spins in Germanium offer the possibility for record manipulation times due to the strong spin-orbit coupling. In addition, they should be largely immune to hyperfine noise.
Here we present electrostatically defined quantum dots hosted in a two-dimensional Germanium hole gas. This approach provides excellent control over the measured system, which we can tune continuously from a single...
A resonant exchange qubit utilizes two orthogonal (S = 1/2, Sz = 1/2) states composed of three electron spins as the qubit states. We realize such a qubit in a GaAs triple quantum dot with each quantum dot hosting a single electron. We couple the electron spins strongly to individual GHz-photons in a strip-line resonator via a tunable electric dipole coupling. Under optimum conditions, the...
High-impedance devices, such as quantum devices, are difficult to measure fast, due to the large impedance mismatch between the quantum device and 50 Ohm wave impedance of RF circuits. Fast and reliable read-out requires impedance matching, which is achieved through a resonant circuit. We compare two approaches, a) a lumped LC- and b) transmission line resonator on a quantum dot (QD) of which...
We investigate a two-dimensional electron system (2DES) embedded in an optical cavity. Cavity photons are strongly coupled to Fermi polarons, which leads to the formation of polaron-polaritons [1, 2, 3]. The light-matter coupling strength is sensitive to the electronic ground state. As the magnetic field is varied, we find that not only the energy of the polariton but also their scattering...
Magic states were introduced in the context of Clifford circuits as a resource that elevates classically simulatable computations to quantum universal capability, while maintaining the same gate set. Here we study magic states in the context of matchgate (MG) circuits, where the notion becomes more subtle, as MGs are subject to locality constraints and also the SWAP gate is not available....
In this work we relate the physics of time to information theory via a simple question: how many bits of information do we gain when we read off the value of a clock?
Our motivation is to understand from an operational point of view how much information clocks provide about time. Doing so would allow us to connect the performance of clocks with basic quantities in physics, such as size,...
Topological insulators are materials that have a gapped bulk energy spectrum but contain protected in-gap states appearing at their surface. These states exhibit remarkable properties such as unidirectional propagation and robustness to noise that offer an opportunity to improve the performance and scalability of quantum technologies. For quantum applications, it is essential that the...
New cutting edge technology developed in Poland allows obtaining the complete information from high energetic photons undergoing Compton scatterings. This in turn enables for the first time to read out the quantum information from the molecular environment, i.e. to study the quantum computing in metabolic processes in human beings. This new information may be related e.g. to cancer in humans...
The development of methods for coherent manipulation of single isolated molecules has made rapid progress in recent years with exciting applications in the fields of precision spectroscopy, fundamental-physics-theories tests, atomic clocks and quantum-controlled chemistry.
In this talk, I will describe our advances for achieving quantum control over a single molecule. In our experiment,...
Atom interferometry has proven within the last decades its surprising versatility to sense with high precision tiniest forces. In this talk I will give an overview of our recent work using an optical cavity enhanced atom interferometer to sense with gravitational strength for fifths forces [1] and for an on the first-place counter-intuitive force due to blackbody radiation[2,3].
[1] M....
We present the novel Long-Baseline Universal Matter-wave Interferometer (LUMI) in Vienna, a near-field, Kapitza-Dirac-Talbot-Lau type interferometer designed for quantum interference of high-mass molecules. It improves on an earlier Kapitza-Dirac-Talbot-Lau interferometer [1] by a factor of 10 in length and a factor 100 in inertial force sensitivity.
The modular design of the experiment...
We are developing a highly compact and high-performance vapor-cell atomic clock operating in time-domain Ramsey scheme [1]. Here, we present an analysis of the dominant contributions to the clock instability at the level of 10$^{-14}$, on long-term timescales up to one day. Main limitations arise from light-shift effects, the barometric effect (i.e. the sensitivity to environmental pressure...
The quantum-to-classical transition is one of the great frontiers of pure physics research. Generating large and long-lived entanglement is a path to exploring it. To reach this path we are using large ensembles of rare-earth ions doped into transparent crystals. Due to their appealing optical and microwave transitions, combined with unparalleled coherence properties, they have been a strong...
Levitodynamics, studying the dynamics of levitated massive particles in vacuum, is currently finding applications in high-end sensing. Within fundamental physics, investigating quantum mechanics or thermodynamics at the mesoscale are driving forces of the emerging field. All these areas of levitodynamics rely on tightest control over the center-of-mass (c.m.) motion of the particle.
Here, we...
