Digital Quantum Simulation of Spin Models with Circuit Quantum Electrodynamics

Salathé, Yves; Mondal, Mintu; Oppliger, Markus; Heinsoo, Johannes; Kurpiers, Philipp; Potočnik, Anton; Mezzacapo, Antonio; Heras, U. Las; Lamata, Lucas; Solano, E.; Filipp, Stefan; Wallraff, Andreas

doi:10.1103/physrevx.5.021027

Cited by 256 publications

(262 citation statements)

References 70 publications

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“…Local operations are a crucial element of a quantum simulator and they have been used, for example, to perform one-qubit rotations for quantum state tomography [2], to engineer two-qubit quantum gates (see e.g. [3,4]), or to prepare peculiar initial states [5,6] and apply local noise [7] for studies of many-body localization. To achieve a local operation, one usually shifts the frequency of one targeted qubit in the system.…”

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confidence: 99%

Optical Control of the Resonant Dipole-Dipole Interaction between Rydberg Atoms

et al. 2017

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We report on the local control of the transition frequency of a spin-1/2 encoded in two Rydberg levels of an individual atom by applying a state-selective light shift using an addressing beam. With this tool, we first study the spectrum of an elementary system of two spins, tuning it from a non-resonant to a resonant regime, where "bright" (superradiant) and "dark" (subradiant) states emerge. We observe the collective enhancement of the microwave coupling to the bright state. We then show that after preparing an initial single spin excitation and letting it hop due to the spin-exchange interaction, we can freeze the dynamics at will with the addressing laser, while preserving the coherence of the system. In the context of quantum simulation, this scheme opens exciting prospects for engineering inhomogeneous XY spin Hamiltonians or preparing spin-imbalanced initial states.Real-world magnetic materials are often modeled with simple spin Hamiltonians exhibiting the key properties under study. Despite their simplified character, these models remain challenging to solve, and an actively explored approach is to implement them in pristine experimental platforms [1]. Such quantum simulators usually require an ordered assembly of interacting spins, also called qubits in the case of spin-1/2, manipulated by global and local coherent operations. Local operations are a crucial element of a quantum simulator and they have been used, for example, to perform one-qubit rotations for quantum state tomography [2], to engineer two-qubit quantum gates (see e.g. [3,4]), or to prepare peculiar initial states [5,6] and apply local noise [7] for studies of many-body localization. To achieve a local operation, one usually shifts the frequency of one targeted qubit in the system. Depending on the physical platform, different approaches are used to accomplish this, such as applying static electric fields for quantum dots [8], or magnetic fluxes for superconducting circuits [9]. In atomic systems, focusing an off-resonant laser beam on a single site can be used to apply an AC-Stark shift on ground-state levels [10][11][12][13].Another promising approach for quantum information science and quantum simulation of spin Hamiltonians are atomic platforms based on Rydberg states [14,15], as they provide strong, tunable dipole-dipole interactions [16][17][18]. In addition, arrays of optical tweezers allow the efficient preparation of assemblies of up to 50 atoms, arranged in arbitrary geometries, as has been recently demonstrated [19,20]. One can encode a spin-1/2 between the ground-state and a Rydberg level, use the van der Waals interactions between two identical Rydberg states and map the system onto an Ising-like Hamiltonian [21]. In this case, the spins can be manipulated globally by a resonant laser field and local addressing has been demonstrated using a far red-detuned focused laser beam shifting the ground-state energy of a particular atom in the ensemble [11].In addition to Ising Hamiltonian, the long-range XY Hamiltonian [22][23][24][25...

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confidence: 99%

Optical Control of the Resonant Dipole-Dipole Interaction between Rydberg Atoms

et al. 2017

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“…and then, apply (50) to each sum with the probabilities given by (7). One arrives at F = Γ(n th , n ↓ ) − Γ(n th , n ↑ ) Γ(n th ) .…”

Section: B Fidelitymentioning

confidence: 99%

Optimal conditions for high-fidelity dispersive readout of a qubit with a photon-number-resolving detector

Sokolov

2016

Phys. Rev. A

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We determine the optimal parameters for a simple and efficient scheme of dispersive readout of a qubit. Depending on the qubit state (ground or excited), the resonance of a cavity is shifted either to the red or to the blue side. Qubit state is inferred by detecting the photon number transmitted through the cavity. It turns out that this kind of detection provides better measurement fidelity than the detection of the presence or absence of photons only. We show that radiating the cavity on either of the frequencies it shifts to results in a suboptimal measurement. The optimal frequency of the probe photons is determined, as well as the optimal ratio of the shift to the resonator leakage. It is shown that to maximize the fidelity of a long-lasting measurement, it is sufficient to use the parameters optimizing the signal-to-noise ratio in the photon count. One can reach 99% fidelity for a single-shot measurement in various physical realizations of the scheme.

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“…Following the method shown in Refs. [30,31], the sign of the qubitqubit coupling coefficients can be reversed by applying a sequence of local qubit rotations. The obtained Hamiltonian is…”

Section: Two-qubit Modelmentioning

confidence: 99%

Ultrastrong-coupling quantum-phase-transition phenomena in a few-qubit circuit QED system

Yang

Wang

2017

Phys. Rev. A

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We study ultrastrong-coupling quantum-phase-transition phenomena in a few-qubit system. In the one-qubit case, three second-order transitions occur and the Goldstone mode emerges under the condition of ultrastrong-coupling strength. Moreover, a first-order phase transition occurs between two different superradiant phases. In the two-qubit case, a two-qubit Hamiltonian with qubit-qubit interactions is analyzed fully quantum mechanically. We show that the quantum phase transition is inhibited even in the ultrastrong-coupling regime in this model. In addition, in the three-qubit model, the superradiant quantum phase transition is retrieved in the ultrastrong-coupling regime. Furthermore, the N -qubit model with U (1) symmetry is studied and we find that the superradiant phase transition is inhibited or restored with the qubit-number parity.

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Digital Quantum Simulation of Spin Models with Circuit Quantum Electrodynamics

Cited by 256 publications

References 70 publications

Optical Control of the Resonant Dipole-Dipole Interaction between Rydberg Atoms

Optical Control of the Resonant Dipole-Dipole Interaction between Rydberg Atoms

Optimal conditions for high-fidelity dispersive readout of a qubit with a photon-number-resolving detector

Ultrastrong-coupling quantum-phase-transition phenomena in a few-qubit circuit QED system

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