- 标题
- 摘要
- 关键词
- 实验方案
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Entanglement Generation in Superconducting Qubits Using Holonomic Operations
摘要： We investigate a nonadiabatic holonomic operation that enables us to entangle two fixed-frequency superconducting transmon qubits attached to a common bus resonator. Two coherent microwave tones are applied simultaneously to the two qubits and drive transitions between the first excited resonator state and the second excited state of each qubit. The cyclic evolution within this effective three-level Λ-type system gives rise to a holonomic operation entangling the two qubits. Two-qubit states with 95% fidelity, limited mainly by charge noise of the current device, are created within 213 ns. This scheme is a step toward implementation of a SWAP-type gate directly in an all-microwave controlled hardware platform. By extending the available set of two-qubit operations in the fixed-frequency qubit architecture, the proposed scheme may find applications in near-term quantum applications using variational algorithms to efficiently create problem-specific trial states. We illustrate this point by computing the ground state of molecular hydrogen using the holonomic operation.
关键词： holonomic operations,microwave control,entanglement,quantum computing,superconducting qubits
更新于2025-09-23 15:23:52
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Verifying multipartite entangled Greenberger-Horne-Zeilinger states via multiple quantum coherences
摘要： The ability to generate and verify multipartite entanglement is an important benchmark for near-term quantum devices. We develop a scalable entanglement metric based on multiple quantum coherences and demonstrate experimentally on a 20-qubit superconducting device. We report a state fidelity of 0.5165 ± 0.0036 for an 18-qubit GHZ state, indicating multipartite entanglement across all 18 qubits. Our entanglement metric is robust to noise and only requires measuring the population in the ground state; it can be readily applied to other quantum devices to verify multipartite entanglement.
关键词： quantum coherence,multipartite entanglement,quantum computing,superconducting qubits,GHZ states
更新于2025-09-23 15:19:57
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Semiclassical analysis of dark-state transient dynamics in waveguide circuit QED
摘要： The interaction between superconducting qubits and one-dimensional microwave transmission lines has been studied experimentally and theoretically in the past two decades. In this work, we investigate the spontaneous emission of an initially excited artificial atom which is capacitively coupled to a semi-infinite transmission line, shorted at one end. This configuration can be viewed as an atom in front of a mirror. The distance between the atom and the mirror introduces a time delay in the system, which we take into account fully. When the delay time equals an integer number of atom oscillation periods, the atom converges into a dark state after an initial decay period. The dark state is an effect of destructive interference between the reflected part of the field and the part directly emitted by the atom. Based on circuit quantization, we derive linearized equations of motion for the system and use these for a semiclassical analysis of the transient dynamics. We also make a rigorous connection to the quantum optics system-reservoir approach and compare these two methods to describe the dynamics. We find that both approaches are equivalent for transmission lines with a low characteristic impedance, while they differ when this impedance is higher than the typical impedance of the superconducting artificial atom.
关键词： quantum optics,circuit quantization,spontaneous emission,dark state,superconducting qubits,microwave transmission lines
更新于2025-09-19 17:13:59
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Electrons in Solids (Mesoscopics, Photonics, Quantum Computing, Correlations, Topology) || 4. Correlated electrons in complex transition metal oxides
摘要： In the previous chapters of this book, we have discussed the consequences of quantum mechanics on the properties of solid state electrons mostly on the single or two particle level. This revealed the important influence of the phase of the electronic wave functions in mesoscopic electronic transport and a general understanding of the optical properties of solids, where the interaction between the electrons led only to relatively simple modifications such as the excitonic binding energy ERyd,X or the dielectric constant of the material ε. In addition, we have learned how to gain an unprecedented control of the quantum mechanical properties, including the dynamics, for single-electron and two-electron systems in spin qubits or in many-particle states in superconducting qubits. There, the electron-electron interaction was mostly used as an exchange coupling or as a classical repulsive energy for read-out.
关键词： spin qubits,electron-electron interaction,mesoscopic electronic transport,excitonic binding energy,superconducting qubits,dielectric constant,solid state electrons,quantum mechanics,optical properties of solids
更新于2025-09-16 10:30:52