Review
Physics, Multidisciplinary
Guido Burkard, Thaddeus D. Ladd, Andrew Pan, John M. Nichol, Jason R. Petta
Summary: The spin degree of freedom of an electron or a nucleus is a basic property that provides a natural two-level system for quantum information processing. Semiconductor spin qubits have made significant advancements in terms of quantum state preparation, coherent control, and measurement. These qubits have the potential for scalable solid-state quantum information processing, thanks to their small size, high density, long coherence times, and existing industrial infrastructure.
REVIEWS OF MODERN PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Rui-Zi Hu, Rong-Long Ma, Ming Ni, Xin Zhang, Yuan Zhou, Ke Wang, Gang Luo, Gang Cao, Zhen-Zhen Kong, Gui-Lei Wang, Hai-Ou Li, Guo-Ping Guo
Summary: This paper introduces how to realize a single spin qubit from Si-MOS quantum dots, including the structure and basic properties of the quantum dots, as well as methods for spin-to-charge conversion and coherent manipulation of spin qubits.
Article
Quantum Science & Technology
Bilal Tariq, Xuedong Hu
Summary: Theoretical investigation shows that the mixing of conduction band valleys greatly affects the exchange interaction in a silicon double quantum dot. The exchange splitting can be suppressed by finite valley phase differences between the dots, and a small valley splitting can result in an incomplete exchange Hamiltonian for low-energy dynamics.
NPJ QUANTUM INFORMATION
(2022)
Article
Multidisciplinary Sciences
Brandon K. Rugg, Kori E. Smyser, Brian Fluegel, Christopher H. Chang, Karl J. Thorley, Sean Parkin, John E. Anthony, Joel D. Eaves, Justin C. Johnson
Summary: The photo-driven process of singlet fission can generate coupled triplet pairs with intriguing properties. Among the sublevels, the quintet is particularly interesting for quantum information. Previous theoretical work has shown that this sublevel can be selectively populated under certain conditions.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
Article
Nanoscience & Nanotechnology
Will Gilbert, Tuomo Tanttu, Wee Han Lim, MengKe Feng, Jonathan Y. Huang, Jesus D. Cifuentes, Santiago Serrano, Philip Y. Mai, Ross C. C. Leon, Christopher C. Escott, Kohei M. Itoh, Nikolay V. Abrosimov, Hans-Joachim Pohl, Michael L. W. Thewalt, Fay E. Hudson, Andrea Morello, Arne Laucht, Chih Hwan Yang, Andre Saraiva, Andrew S. Dzurak
Summary: This study demonstrates fast electrical control of electron spin in silicon quantum dots by exploiting the switchable interaction between spin and orbital motion of electrons without using a micromagnet. By controlling the energy quantization of electrons in nanostructures, the weak effects of the relativistic spin-orbit interaction in silicon are enhanced, leading to a significant increase in Rabi frequency. The achieved coherence time, gate performance, and gate fidelity show the potential for high-performance all-electrical control in scalable silicon quantum computing.
NATURE NANOTECHNOLOGY
(2023)
Article
Optics
S. Omkar, Y. S. Teo, Seung-Woo Lee, H. Jeong
Summary: We investigate a scheme for topological quantum computing using optical hybrid qubits and show an improved photon loss threshold. By creating a special cluster state, known as Raussendorf lattice, the threshold is enhanced up to 5.7 x 10(-3). Although this improvement comes with increased resource consumption compared to previous schemes, it remains more resource-efficient compared to other known optical schemes for fault-tolerant quantum computation.
Article
Multidisciplinary Sciences
Aaron J. Weinstein, Matthew D. Reed, Aaron M. Jones, Reed W. Andrews, David Barnes, Jacob Z. Blumoff, Larken E. Euliss, Kevin Eng, Bryan H. Fong, Sieu D. Ha, Daniel R. Hulbert, Clayton A. C. Jackson, Michael Jura, Tyler E. Keating, Joseph Kerckhoff, Andrey A. Kiselev, Justine Matten, Golam Sabbir, Aaron Smith, Jeffrey Wright, Matthew T. Rakher, Thaddeus D. Ladd, Matthew G. Borselli
Summary: This study demonstrates an alternative approach to quantum computation that uses energy-degenerate encoded qubit states controlled by nearest-neighbour contact interactions, bypassing microwave-associated correlated errors. The combination of enriched silicon, all-electrical partial swap operations, and configurable encoding offers a strong pathway towards scalable fault tolerance and computational advantage.
Article
Chemistry, Multidisciplinary
Maximilian Maylander, Su Chen, Emmaline R. Lorenzo, Michael R. Wasielewski, Sabine Richert
Summary: The study investigates the potential of photogenerated molecular spin systems in quantum information science, demonstrating the formation of a quartet state with long spin polarization lifetimes and coherence times, as well as over 60 single-qubit logic operations that can be performed at 80 K. The large magnitude of the nitroxide N-14 hyperfine coupling and the further splitting of electron spin sublevels are also discussed in the context of the system's viability as a qubit for quantum information science applications containing 12 electron-nuclear spin states.
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
(2021)
Article
Materials Science, Multidisciplinary
Maria Spethmann, Xian-Peng Zhang, Jelena Klinovaja, Daniel Loss
Summary: Superconducting spin qubits, coupled to each other via a superconductor, demonstrate fast controlled phase-flip gates. The effective interaction between these qubits can be adjusted by the superconducting phase difference, the tunnel barrier strength, or the spin-orbit interaction parameters.
Article
Quantum Science & Technology
F. van Riggelen, W. I. L. Lawrie, M. Russ, N. W. Hendrickx, A. Sammak, M. Rispler, B. M. Terhal, G. Scappucci, M. Veldhorst
Summary: The study demonstrates the feasibility of implementing quantum error correction codes using a four-qubit array in germanium and successfully demonstrates key quantum gate operations. Although significant improvement in the quality and quantity of qubits is needed, the implementation of quantum error correction codes enables co-design development of quantum hardware and software.
NPJ QUANTUM INFORMATION
(2022)
Article
Multidisciplinary Sciences
Yi-Han Luo, Ming-Cheng Chen, Manuel Erhard, Han-Sen Zhong, Dian Wu, Hao-Yang Tang, Qi Zhao, Xi-Lin Wang, Keisuke Fujii, Li Li, Nai-Le Liu, Kae Nemoto, William J. Munro, Chao-Yang Lu, Anton Zeilinger, Jian-Wei Pan
Summary: Quantum gate teleportation proposes an elegant solution to replace fragile nontransverse inline gates with specific highly entangled offline resource states for implementing nontransverse gates in circuits. By creating maximally entangled states and teleporting quantum information, the scheme can achieve fidelities up to 0.786 and be fully fault tolerant for future large-scale quantum technologies.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2021)
Article
Physics, Multidisciplinary
Matthew Rogers, Alistair Walton, Machiel G. Flokstra, Fatma Al Ma'Mari, Rhea Stewart, Stephen L. Lee, Thomas Prokscha, Andrew J. Caruana, Christian J. Kinane, Sean Langridge, Harry Bradshaw, Timothy Moorsom, Mannan Ali, Gavin Burnell, Bryan J. Hickey, Oscar Cespedes
Summary: The combination of magnetic molecules with a metallic substrate allows for the manipulation of molecular spin properties and potential application in low-power information storage devices. Research demonstrates the feasibility of achieving spin-ordering and superconducting properties at the metallo-molecular interface, enabling lower energy spin transfer and magnetic switching in quantum computing and information storage. The results showcase the potential of metallo-molecular interfaces for singlet to triplet Cooper pair conversion, offering a new capability for generating and controlling the diffusion of spin polarized dissipationless currents.
COMMUNICATIONS PHYSICS
(2021)
Article
Quantum Science & Technology
Alexandre M. Souza
Summary: In this study, dynamical decoupling sequences were tested on a single qubit using the Rigetti quantum computing platform. It was found that pulse imperfections limited the performance, but using robust sequences improved the effectiveness of dynamical decoupling. The tested sequences outperformed previous ones on the same platform.
QUANTUM INFORMATION PROCESSING
(2021)
Article
Quantum Science & Technology
Kaixuan Huang, Zheng-An Wang, Chao Song, Kai Xu, Hekang Li, Zhen Wang, Qiujiang Guo, Zixuan Song, Zhi-Bo Liu, Dongning Zheng, Dong-Ling Deng, H. Wang, Jian-Guo Tian, Heng Fan
Summary: Generative adversarial networks have been successful in machine learning, and their quantum counterparts, known as quantum generative adversarial networks (QGANs), may have exponential advantages. Researchers have implemented a QGAN using a programmable superconducting processor, paving the way for experimental explorations of quantum advantages in practical applications with near-term quantum technologies.
NPJ QUANTUM INFORMATION
(2021)
Review
Chemistry, Multidisciplinary
Andre Saraiva, Wee Han Lim, Chih Hwan Yang, Christopher C. Escott, Arne Laucht, Andrew S. Dzurak
Summary: Quantum computers have the potential to solve problems in multiple industries efficiently, but require millions of qubits for error correction. Silicon quantum dots with electron spins are strong contenders for encoding qubits, but commercially manufactured transistors may have a different impact on their performance.
ADVANCED FUNCTIONAL MATERIALS
(2022)
Article
Quantum Science & Technology
Regina Finsterhoelzl, Guido Burkard
Summary: We evaluate the performance of small error-correcting codes tailored to different hardware platforms, taking into account hardware-specific errors and connectivity. We investigate the dependence of logical error rate on platform features and benchmark our predictions with experimental results. The results show that the quasi-linear layout of superconducting devices is advantageous for small codes, while the central-spin connectivity of color centers enables lower error rates for codes involving multi-qubit controlled operations.
QUANTUM SCIENCE AND TECHNOLOGY
(2023)
Article
Physics, Multidisciplinary
Tobias Bonsen, Patrick Harvey -Collard, Maximilian Russ, Jurgen Dijkema, Amir Sammak, Giordano Scappucci, Lieven M. K. Vandersypen
Summary: We report on observations of transitions between excited states in the Jaynes-Cummings ladder of circuit quantum electrodynamics with electron spins (spin circuit QED). Unexplained features in recent experimental work are found to correspond to these transitions, and an input-output framework that incorporates these effects is presented. New experiments reproduce previous observations and demonstrate excited-state transitions and multiphoton transitions by increasing the probe power and using two-tone spectroscopy. The ability to probe the Jaynes-Cummings ladder is facilitated by improvements in the coupling-to-decoherence ratio, highlighting the increased maturity of spin circuit QED as an intriguing platform for studying quantum phenomena.
PHYSICAL REVIEW LETTERS
(2023)
Review
Physics, Multidisciplinary
Guido Burkard, Thaddeus D. Ladd, Andrew Pan, John M. Nichol, Jason R. Petta
Summary: The spin degree of freedom of an electron or a nucleus is a basic property that provides a natural two-level system for quantum information processing. Semiconductor spin qubits have made significant advancements in terms of quantum state preparation, coherent control, and measurement. These qubits have the potential for scalable solid-state quantum information processing, thanks to their small size, high density, long coherence times, and existing industrial infrastructure.
REVIEWS OF MODERN PHYSICS
(2023)
Article
Multidisciplinary Sciences
Brian Paquelet Wuetz, Davide Degli Esposti, Anne-Marije J. Zwerver, Sergey V. Amitonov, Marc Botifoll, Jordi Arbiol, Lieven M. K. Vandersypen, Maximilian Russ, Giordano Scappucci
Summary: Improving the material stack of gate-defined quantum dots in Si-28/SiGe heterostructure is crucial for reducing charge noise in the host semiconductor. By studying the semiconductor-dielectric interface and the buried quantum well, it is found that enhancements in scattering properties and uniformity of the two-dimensional electron gas result in a significant reduction in charge noise. Extrapolating the measured charge noise to simulated dephasing times shows a potential improvement in CZ-gate fidelities by nearly one order of magnitude.
NATURE COMMUNICATIONS
(2023)
Article
Physics, Applied
Brennan Undseth, Xiao Xue, Mohammad Mehmandoost, Maximilian Rimbach-Russ, Pieter T. Eendebak, Nodar Samkharadze, Amir Sammak, Viatcheslav V. Dobrovitski, Giordano Scappucci, Lieven M. K. Vandersypen
Summary: Micromagnet-based electric dipole spin resonance is a promising method for scaling silicon spin qubits in gate-defined quantum dots, while maintaining long coherence times and high control fidelities. However, understanding and mitigating cross-talk mechanisms is crucial for accurately controlling dense arrays of qubits using a multiplexed drive. We identified an unexpected cross-talk mechanism where the Rabi frequency of a driven qubit is significantly affected by the drive of an adjacent qubit. These findings have important implications for scaling single-qubit control.
PHYSICAL REVIEW APPLIED
(2023)
Article
Quantum Science & Technology
Violeta N. N. Ivanova-Rohling, Niklas Rohling, Guido Burkard
Summary: Quantum state tomography is an essential tool for evaluating and validating quantum processors. In ideal scenarios, optimal measurement sets for tomography can be analytically determined, but in other cases, numerical approximation is needed. This study introduces a customized efficient tomography framework to find the optimal measurement set in the presence of noisy quantum gates. The results show that using entangling gates improves the accuracy of tomography reconstruction at realistic noise levels.
EPJ QUANTUM TECHNOLOGY
(2023)
Article
Quantum Science & Technology
A. M. J. Zwerver, S. Amitonov, S. L. de Snoo, M. T. Madzik, M. Rimbach-Russ, A. Sammak, G. Scappucci, L. M. K. Vandersypen
Summary: Coherent links between distant spin qubits can be achieved by shuttling the electron spin through an array of quantum dots. In this experiment, we move an electron spin through a linear array of four tunnel-coupled quantum dots by adjusting the electrochemical potential for each dot. The estimated spin-flip probability per hop is below 0.01% based on the experimental results.
Article
Optics
Jannis Ruh, Regina Finsterhoelzl, Guido Burkard
Summary: The paper presents a quantum algorithm for digital quantum simulations of the BCS model on a quantum register with a star-shaped connectivity map. The translation of the problem onto the quantum hardware and implementation using native interactions between qubits are discussed, along with the circuit complexity. The algorithm is used to simulate the dynamics of the BCS model and is studied using classical simulations.
Article
Optics
Philipp M. Mutter, Guido Burkard
Summary: We develop a theory to describe the transient transmission through noisy qubit-resonator systems, where quadratic interactions are present in superconducting and nanomechanical resonators coupled to solid-state qubits. By generalizing the quantum Langevin equations, we find that only linear and quadratic couplings allow for an analytical treatment using standard input-output theory. Focusing on quadratic couplings and arbitrary initial qubit coherences, we demonstrate that noise characteristics can be extracted from input-output measurements by analyzing the averaged fluctuations in transmission probability and phase. Our results extend the field of transmission-based noise spectroscopy and have immediate practical applications.
Article
Materials Science, Multidisciplinary
Balazs Gulacsi, Guido Burkard
Summary: We describe temporally correlated noise processes that influence the idle evolution of a superconducting transmon qubit. Based on quantum circuit theory, we model the composite qubit-environment system and derive a circuit Hamiltonian for transverse noise affecting the qubit. Using the time-convolutionless projection operator method, we construct a time-local master equation that exhibits eternally non-Markovian dynamics. By expressing the solution of the master equation in the Kraus representation, we identify two crucial non-Markovian phenomena: periodic revivals of coherence and the appearance of additional frequencies far from the qubit frequency.
Article
Optics
Joris Kattemoelle, Guido Burkard
Summary: The quantum approximate optimization algorithm (QAOA) has the potential to provide quantum advantage on noisy intermediate-scale quantum (NISQ) devices. Recent experimental results show that the errors impacting NISQ devices are significantly correlated. A model for spatially and temporally correlated errors based on classical environmental fluctuators is introduced. The study finds evidence that the performance of QAOA improves as the correlation time or correlation length of the noise increases at fixed local error probabilities, suggesting that noise correlations need not be detrimental for NISQ algorithms like QAOA.
Article
Materials Science, Multidisciplinary
Florian Ginzel, Guido Burkard
Summary: Both quantum transport measurements in the Pauli blockade regime and microwave cavity transmission measurements are important tools for spin-qubit readout and characterization. A theoretical framework is derived to investigate how a double quantum dot interacts with a coupled microwave resonator while the current through the dot is rectified by Pauli blockade. The output field of the resonator can be used to infer the leakage current and obtain insight into the blockade mechanisms, providing detailed knowledge about the microscopic environment of the dot.
Article
Materials Science, Multidisciplinary
Jonas Mielke, Guido Burkard
Summary: Nuclear spins have long coherence times, but isolating them from the environment for controlling nuclear spin qubits is challenging. Strong coupling between an electron spin and microwave resonator photons, as well as microwave resonator mediated coupling between two electron spins, has been reported. Inspired by these findings, we theoretically investigate the interaction of a microwave resonator with a hybrid quantum dot-donor (QDD) system. By driving the QDD system, we can compensate the frequency mismatch and enable effective nuclear spin-photon coupling. Coupling the nuclear spins of two distant QDD systems to the microwave resonator allows the implementation of a resonator-mediated nuclear spin two-qubit iSWAP gate with a gate fidelity approaching 90%.
Article
Physics, Multidisciplinary
T. L. M. Guedes, I Vakulchyk, D. V. Seletskiy, A. Leitenstorfer, A. S. Moskalenko, Guido Burkard
Summary: The influence of measurement back action on electro-optic sampling of electromagnetic quantum fluctuations is investigated. Based on a cascaded treatment of the nonlinear interaction between a near-infrared coherent probe and the mid-infrared vacuum, we account for the generated electric-field contributions that lead to detectable back action. The setup parameters at which back action starts to considerably contaminate the measured noise profiles are determined. We find that back action starts to detrimentally affect the signal once the fluctuations due to the coupling to the mid-infrared vacuum become comparable to the base shot noise. Due to the vacuum fluctuations entering at the beam splitter, the shot noise of two incoming probe pulses in different channels is uncorrelated. Therefore, even when the base shot noise dominates the output of the experiment, it does not contribute to the correlation signal itself. However, we find that further contributions due to nonlinear shot-noise enhancement are still present. Ultimately, a regime in which electro-optic sampling of quantum fields can be considered as effectively back-action free is found.
PHYSICAL REVIEW RESEARCH
(2023)
