A5046690505- Advanced MIMO Systems Optimization
- Cooperative Communication and Network Coding
- Energy Harvesting in Wireless Networks
- Wireless Communication Security Techniques
- Advanced Wireless Network Optimization
- Quantum Information and Cryptography
- Quantum Computing Algorithms and Architecture
- Advanced Wireless Communication Techniques
- Quantum and electron transport phenomena
- Blind Source Separation Techniques
- Neural Networks and Reservoir Computing
- Wireless Communication Networks Research
- Photonic and Optical Devices
- Distributed Sensor Networks and Detection Algorithms
- Atomic and Subatomic Physics Research
- Statistical Mechanics and Entropy
- Wireless Body Area Networks
- Control Systems and Identification
- Sparse and Compressive Sensing Techniques
- Target Tracking and Data Fusion in Sensor Networks
- Cold Atom Physics and Bose-Einstein Condensates
- Millimeter-Wave Propagation and Modeling
- Quantum-Dot Cellular Automata
- Photocathodes and Microchannel Plates
- Direction-of-Arrival Estimation Techniques
ETH Zurich
2020-2025
Institut für Informationsverarbeitung
2015-2021
Technical University of Munich
2011-2021
Quantum computing crucially relies on the ability to efficiently characterize quantum states output by hardware. Conventional methods which probe these through direct measurements and classically computed correlations become computationally expensive when increasing system size. neural networks tailored recognize specific features of combining unitary operations, feedforward promise require fewer tolerate errors. Here, we realize a convolutional network (QCNN) 7-qubit superconducting...
Variational quantum algorithms are believed to be promising for solving computationally hard problems on noisy intermediate-scale (NISQ) systems. Gaining computational power from these critically relies the mitigation of errors during their execution, which coherence-limited operations is achievable by reducing gate count. Here, we demonstrate an improvement up a factor 3 in algorithmic performance approximate optimization algorithm (QAOA) as measured success probability, implementing...
The performance of a wide range quantum computing algorithms and protocols depends critically on the fidelity speed employed qubit readout. Examples include gate sequences benefiting from midcircuit real-time measurement-based feedback, such as initialization, entanglement generation, teleportation, and, perhaps most importantly, error correction. A prominent widely used readout approach is based dispersive interaction superconducting strongly coupled to large-bandwidth resonator, frequently...
A major challenge in operating multi-qubit quantum processors is to mitigate coherent errors. For superconducting circuits, besides crosstalk originating from imperfect isolation of control lines, dispersive coupling between qubits a source We benchmark phase errors controlled-phase gate due either the involved one or more spectator qubits. measure associated infidelity using process tomography. In addition, we point out that, non-computational state during gate, two-qubit conditional are...
Quantum error correction is needed for quantum computers to be capable of fault-tolerantly executing algorithms using hundreds logical qubits. Recent experiments have demonstrated subthreshold rates state preservation a single qubit. In addition, the realization universal computation requires implementation entangling gates. Lattice surgery offers practical approach implementing such gates, particularly in planar processor layouts. this work, we demonstrate lattice between two distance-three...
The use of proper, i.e., circularly symmetric, complex Gaussian signals for all users is known to be optimal in broadcast channels with proper noise from an information theoretic point view, they are employed the capacity-achieving strategy. However, such per-user transmit not necessarily problems quality-of-service (QoS) constraints if strategy restricted widely linear transceivers without time-sharing. This shown by deriving QoS feasibility region multiple-input multiple-output channel...
Two main lines of approach can be identified in the recent literature on improper signals and widely linear operations. The augmented complex formulation based signal its conjugate is considered as more insightful since it leads to convenient mathematical formulations for many problems. Moreover, allows an easy distinction between proper well On other hand, composite real representation using imaginary parts closer actual implementation, readily reuse results that have originally been...
While globally optimal solutions to many convex programs can be computed efficiently in polynomial time, this is, general, not possible for nonconvex optimization problems. Therefore, locally approaches or other efficient suboptimal heuristics are usually applied practical implementations. However, there is also a strong interest computing of problems offline simulations order benchmark the faster algorithms. Global often rely on monotonicity properties. A common approach reformulate into...
Proper Gaussian signals have been shown to be optimal in multiple-input multiple-output (MIMO) broadcast channels from an information theoretic point of view, i.e., capacity can achieved with a strategy that transmits circularly symmetric complex signals. In this work, we show optimality proper does not necessarily hold if the transmit is restricted widely linear transceivers. The proof performed by identifying rate tuple achievable certain set transceivers and improper signals, but lies...
For Gaussian multiple-input multiple-output (MIMO) relay channels with partial decode-and-forward, the optimal type of input distribution is still an open question in general. Recent research has revealed that some other scenarios unknown distributions (e.g., interference channels), improper (i.e., noncircular) can outperform proper (circular) distributions. In this paper, we show not case for decode-and-forward MIMO channel transmit signals, i.e., a one among all order to prove property,...
We consider the communication over a set of parallel multiple-input single-output (MISO) broadcast channels with separate linear precoding on each them. In this setup, we study problem fulfilling per-user quality service constraints, expressed in terms rates, using minimal transmit power. By means dual decomposition approach and branch-and-bound algorithm solving arising nonconvex subproblems, find so far unknown globally optimal solution for case time sharing. Although prohibitively complex...
We study the problem of minimizing sum transmit power in mutliple-input multiple-output (MIMO) downlink channels with linear transceivers if per-user quality service (QoS) constraints (expressed terms rates) have to be fulfilled. To find a suboptimal solution arising non-convex optimization problem, we introduce new auxiliary variables representing di- vision rate into per-stream targets, and optimize these by means gradient-projection steps. This method is combined alternating updates...
It has recently been shown that improper signaling enlarges the rate region of Gaussian single-antenna one-sided interference channel (Z-interference channel, ZIFC) under assumptions all input signals are and is treated as noise. was pointed out this result also holds if time-sharing between different operation points allowed. However, existing literature considered problem only for short-term average power constraints, i.e., transmit powers limited individually in each time slot. We...
So-called improper complex signals have been shown to be beneficial in the single-antenna two-user Gaussian interference channel under assumptions that all input are and we treat as noise (TIN). This result has obtained a restriction pure strategies without time-sharing, it was extended case where rates, but not transmit powers, may averaged over several strategies. In this paper, drop such restrictions discuss most general of coded both rates powers averaged. Since time-sharing can...
In the two-user Gaussian interference channel (IFC) with inputs and treating as noise (TIN), it depends on assumptions about time-sharing whether improper signals (asymmetric complex signals) can bring benefits over proper signals. If no is allowed (pure strategies) or convex hull formulation used (only data rates be averaged), signaling lead to a larger rate region than optimal signaling. However, when coded allowed, i.e., both transmit powers averaged, whole achieved by Here, we show that...
The ability to execute high-fidelity operations is crucial scaling up quantum devices large numbers of qubits. However, signal distortions originating from nonlinear components in the control lines can limit performance single-qubit gates. In this work, we use a measurement based on error amplification characterize and correct small rotation errors qubit drive rate with amplitude programmed pulse. With our hardware, for 15-ns pulse, angles deviate by several degrees linear model. Using...
Josephson traveling-wave parametric amplifiers (TWPAs) enable the amplification of weak microwave signals close to quantum limit with large bandwidth, which has a broad range applications in superconducting computing and operation single-photon detectors. While bandwidth allows for their use frequency-multiplexed detection architectures, an increased number readout tones per amplifier puts more stringent requirements on dynamic avoid saturation. Here, we characterize undesired mixing...
Recently, a neural-network-based method for massive MIMO uplink channel estimation was introduced. The derivations assumed uniform linear array (ULA) with half-wavelength antenna spacing at the base station. In this work, we show that estimator can also be used in case of ULAs and rectangular arrays (URAs) spacings given by integer multiples half wavelength. We then investigate how certain parameters model influence performance.
Parallel multiple-input multiple-output (MIMO) broadcast channels have been shown to be separable from an information theoretic point of view, i.e., capacity can achieved with a strategy that performs separate encoding and decoding on each subchannel subject power allocation across subchannels. In this paper, we show separability does not necessarily hold if the transmit is restricted linear transceivers. The proof will done by identifying rate tuple achievable in certain set joint treatment...
Principal component analysis (PCA) is a tool for dimensionality reduction, feature extraction, and data compression, which applied to both real-valued complex-valued sets. For complex data, modified version of PCA based on widely linear transformations was shown be beneficial if the considered random variables are improper, i.e., in case correlations or power imbalances between real imaginary parts. This approach formulated an augmented representation existing literature. In this paper, we...
We consider the maximization of energy efficiency (or, equivalently, minimization per bit) in a set parallel multiple-input single-output (MISO) broadcast channels (e.g., downlink multiuser multicarrier system). For given allocation users to subchannels, problem is strictly-quasiconvex and can be efficiently solved by introducing continuous, differentiable, concave waterfilling-rate function. To optimize user allocation, we adopt successive schemes that have been formerly applied sum rate...
The rate balancing problem is considered in the multiple-input single-output (MIMO) broadcast channel with linear transceivers. After introducing relative per-stream targets as auxiliary variables, optimization performed by a gradient projection algorithm. In addition, transmit and receive filters are updated mean square error matrices diagonalized each iteration. Although algorithm can only find local optima of non-convex problem, numerical simulations show that it achieves good performance...