Article
Materials Science, Multidisciplinary
Stephen R. McMillan, Guido Burkard
Summary: A critical element for scalable quantum processors is the nonlocal coupling between nodes. Recent research has shown that spin-based qubits in double quantum dot architectures can exhibit spin-spin interactions via the exchange of photons. This study proposes a framework for a resonant direct-CNOT operation between nonlocal single-spin qubits.
Article
Quantum Science & Technology
Amor Gueddana, Vasudevan Lakshminarayanan
Summary: We propose a Controlled-Controlled-phase gate (CCZ) using three atoms trapped in separate optical cavities and connected by two optical fibers. We analyze the Hamiltonian of the atom-cavity-fiber system and provide Hamiltonian matrix expressions for different initial states. We study the fidelity of the gate and show that it can reach 99.28%, considering the impact of physical parameters and factors such as spontaneous emission and photon leakage.
QUANTUM INFORMATION PROCESSING
(2022)
Article
Nanoscience & Nanotechnology
A. Chiesa, F. Petiziol, E. Macaluso, S. Wimberger, P. Santini, S. Carretta
Summary: A scalable architecture for quantum computing relies on logical units that support quantum-error correction, with magnetic molecules showing promise in defining logical qubits with embedded quantum-error correction. This single-object encoding is expected to simplify error correction procedures and logical operations, as demonstrated by implementing two-qubit gates between error-protected units using easily implementable sequences of electro-magnetic pulses.
Article
Quantum Science & Technology
Federico Fedele, Anasua Chatterjee, Saeed Fallahi, Geoffrey C. Gardner, Michael J. Manfra, Ferdinand Kuemmeth
Summary: Researchers demonstrated a two-by-two array of four singlet-triplet qubits in gallium arsenide, showing simultaneous coherent operations and four-qubit measurements via exchange oscillations and frequency-multiplexed single-shot measurements. A larger multielectron quantum dot is fabricated in the center of the array as a tunable interqubit link, which is utilized to demonstrate coherent spin exchange with selected qubits. These techniques can be extended to other materials, showing a path towards quantum processors with gate-controlled spin qubits.
Article
Optics
Qi-Ping Su, Yu Zhang, Chui-Ping Yang
Summary: This study proposes a one-step implementation of a multi-target qubit controlled-NOT gate, where a superconducting qubit controls multiple cat-state qubits simultaneously. The gate operation is simple, quick, and independent of the number of target qubits.
Article
Physics, Multidisciplinary
Kai Zhou, Cheng Zhang, Lupei Qin, Xin-Qi Li
Summary: In this study, the performance of a double-dot interferometer under environmental noise was analyzed for the quantum measurement of Majorana qubits and surface-code stabilizers. The double-dot setup design allowed for consideration of the full multiple tunneling process through the Majorana island using a master equation approach. Analytic solutions for the measurement currents were obtained in the co-tunneling regime, providing insight for future experiments on Majorana qubits and stabilizer measurements.
Article
Chemistry, Multidisciplinary
Marek Korkusinski, Yasser Saleem, Amintor Dusko, Daniel Miravet, Pawel Hawrylak
Summary: We predict the existence of spontaneous spin and valley symmetry-broken states in a gated bilayer graphene quantum dot. By exact diagonalization of the many-body Hamiltonian, we find that the electron system undergoes phase transitions with increasing spin and valley polarizations as the Coulomb interaction strength increases. A phase diagram for N = 1-6 electrons is mapped out as a function of the Coulomb interaction strength.
Article
Multidisciplinary Sciences
Thomas McJunkin, Benjamin Harpt, Yi Feng, Merritt P. Losert, Rajib Rahman, J. P. Dodson, M. A. Wolfe, D. E. Savage, M. G. Lagally, S. N. Coppersmith, Mark Friesen, Robert Joynt, M. A. Eriksson
Summary: This study proposes a new heterostructure, the Wiggle Well, which uses concentration oscillations of Ge in the quantum well to enhance the valley splitting of quantum-dot spin qubits. The experimental results show that the presence of Ge in the quantum well does not affect the formation and manipulation of single-electron quantum dots. It is suggested that the enhancement of the valley splitting is mainly attributed to random concentration fluctuations and the presence of Ge alloy.
NATURE COMMUNICATIONS
(2022)
Article
Physics, Multidisciplinary
Qi-Ping Su, Yu Zhang, Liang Bin, Chui-Ping Yang
Summary: This study proposes an efficient scheme to implement multiple photonic qubits controlling one target qubit simultaneously. The scheme is simple and general, with advantages such as avoiding decoherence from auxiliary levels.
FRONTIERS OF PHYSICS
(2022)
Article
Physics, Condensed Matter
Constantine Yannouleas, Uzi Landman
Summary: The exact diagonalization of the microscopic many-body Hamiltonian using FCI calculations accurately predicts the spectra of three-electron hybrid qubits based on GaAs double quantum dots. These spectroscopic patterns are closely related to the formation of Wigner molecules due to strong inter-electron correlations. Previous theoretical models cannot capture these physical entities.
JOURNAL OF PHYSICS-CONDENSED MATTER
(2022)
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
Physics, Applied
Y. F. Wang, W. P. Gao, K. Liu, B. Ji, Z. Wang, Z. R. Lin
Summary: In this work, a practical SFQ-based two-qubit gate for transmon qubits is presented. The CZ gate is activated by near-resonant SFQ-pulse trains near the target transition involving the second excited state. Numerical simulations show that a SFQ-activated CZ gate with a fidelity exceeding 99.9% can be achieved within a gate time of 100 ns. Combined with proposed expansion methods, this work serves as a supplement to the scalable and integratable superconducting-qubit control system based on SFQ digital logic.
PHYSICAL REVIEW APPLIED
(2023)
Article
Materials Science, Multidisciplinary
Guo Xuan Chan, J. P. Kestner, Xin Wang
Summary: Theoretically, a range of nearly sweet spots appears in the coupled singlet-triplet qubit system when a strong enough external magnetic field is applied. Ramping to and from the judiciously chosen nearly sweet spot using sequences based on the shortcut to adiabaticity offers maximal gate fidelities under charge noise and phonon-induced decoherence, facilitating realization of high-fidelity two-qubit gates in singlet-triplet qubit systems.
Article
Physics, Multidisciplinary
Iann Cunha, Leonardo Kleber Castelano
Summary: This study investigates the impact of the ability to connect distant qubits on the performance of quantum computing systems. By using a spin chain model and swap gates, interactions between quantum bits are implemented, and these gates are applied in a decoherence-free system to improve fidelity. The results show that the order of swap gates and CNOT gates is crucial for fidelity when the number of qubits is large.
Article
Optics
Qianyu Zhu, Cheng Lu, Jin-Lei Wu, Yan Li
Summary: Soft quantum control is a powerful technique that allows for highly selective interactions in quantum systems. In this study, a model is proposed for implementing a controlled-Z (CZ) gate in superconducting circuit quantum electrodynamics. The CZ gate is induced between two qubits by employing an external classical field and the strong single-mode quantized cavity field. The gate is further optimized using a Gaussian soft control (GSC), which improves its performance in various aspects compared to a rectangular pulse.
LASER PHYSICS LETTERS
(2022)
