Implementation of Conditional Phase Gates Based on Tunable 
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Collodo, Michele C.; Herrmann, J.; Lacroix, Nathan; Andersen, Christian Kraglund; Remm, Ants; Lazar, Stefania; Besse, Jean-Claude; Walter, Theo; Wallraff, Andreas; Eichler, Christopher

doi:10.1103/physrevlett.125.240502

Cited by 126 publications

(96 citation statements)

References 51 publications

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“…C). Meanwhile, each coupler is dynamically switched between two frequencies [58][59][60][61][62][63]: one is to turn off the effective coupling where the neighboring two qubits can be initialized and operated with single-qubit gates; the other one is to turn on the nearest-neighbor coupling to around 11 MHz for a CZ gate. After n layers of the alternating single-and two-qubit gates, we finally tune all qubits to their respective ω m j for simultaneous quantum-state measurement.…”

Section: Methodsmentioning

confidence: 99%

Observation of a Floquet symmetry-protected topological phase with superconducting qubits

Deng

Zhang

Jiang

et al. 2021

Preprint

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Quantum many-body systems away from equilibrium host a rich variety of exotic phenomena that are forbidden by equilibrium thermodynamics. A prominent example is that of discrete time crystals [1-8], where time translational symmetry is spontaneously broken in periodically driven systems. Pioneering experiments have observed signatures of time crystalline phases with trapped ions [9,10], spins in nitrogen-vacancy centers [11-13], ultracold atoms [14,15], solid spin ensembles [16,17], and superconducting qubits [18-20]. Here, we report the observation of a distinct type of intrinsically non-equilibrium state of matter, a Floquet symmetry-protected topological phase, which is implemented through digital quantum simulation with an array of programmable superconducting qubits. Unlike the discrete time crystals reported in previous experiments, where spontaneous breaking of the discrete time translational symmetry occurs for local observables throughout the whole system, the Floquet symmetry-protected topological phase observed in our experiment breaks the time translational symmetry only at the boundaries and has trivial dynamics in the bulk. More concretely, we observe robust long-lived temporal correlations and sub-harmonic temporal response for the edge spins over up to 40 driving cycles using a circuit whose depth exceeds 240. We demonstrate that the sub-harmonic response is independent of whether the initial states are random product states or symmetry-protected topological states, and experimentally map out the phase boundary between the time crystalline and thermal phases. Our work paves the way to exploring novel non-equilibrium phases of matter emerging from the interplay between topology and localization as well as periodic driving, with current noisy intermediate-scale quantum processors [21].

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Section: Methodsmentioning

confidence: 99%

Observation of a Floquet symmetry-protected topological phase with superconducting qubits

Deng

Zhang

Jiang

et al. 2021

Preprint

View full text Add to dashboard Cite

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“…However, this tunability is usually achieved at the cost of introducing additional decoherence or circuit complexity. [ 70–76 ] Alternatively, parametric modulation of qubits' frequencies can be used to realize this tunability [ 77–79 ] without coupling devices, and thus simplifies the circuit.…”

Section: Parametric Couplingsmentioning

confidence: 99%

“…[ 73 ] Alternatively, the cross‐Kerr ZZ‐interaction can be obtained for two qubits with large qubit‐frequency difference, and, in this case, controlled‐phase gates can be implemented. [ 74,75 ] As the total interaction is adjusted from large detuned qubit‐coupler interaction, the unwanted qubit interactions can also be completely turned off, and thus high‐fidelity quantum operations can be possible.…”

Section: Parametric Couplingsmentioning

confidence: 99%

Topological Photonics on Superconducting Quantum Circuits with Parametric Couplings

Xue

2021

Adv Quantum Tech

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Topological phases of matter are an exotic phenomenon in modern condensed matter physics, which has attracted much attention due to the unique boundary states and transport properties. Recently, this topological concept in electronic materials has been exploited in many other fields of physics. Motivated by designing and controlling the behavior of electromagnetic waves in optical, microwave, and sound frequencies, topological photonics emerges as a rapid growing research field. Due to the flexibility and diversity of superconducting quantum circuits system, it is a promising platform to realize exotic topological phases of matter and to probe and explore topologically‐protected effects in new ways. Here, theoretical and experimental advances of topological photonics on superconducting quantum circuits—via the experimentally demonstrated parametric tunable coupling techniques, including using of the superconducting transmission line resonator, superconducting qubits, and their coupled system—are reviewed. On superconducting circuits, the flexible interactions and intrinsic nonlinearity make topological photonics in this system not only a simple photonic analog of topological effects for novel devices, but also a realm of exotic but less‐explored fundamental physics.

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“…In parallel, coupling strengths have reduced to J 2 =2π ∼ 10-20 MHz to mitigate residual ZZ coupling, which affects single-qubit gates and idling at bias points, and produces crosstalk from spectator qubits [22]. Many groups are actively developing tunable coupling schemes to suppress residual coupling without incurring slowdown [23][24][25][26][27].…”

mentioning

confidence: 99%

High-Fidelity Controlled- Z Gate with Maximal Intermediate Leakage Operating at the Speed Limit in a Superconducting Quantum Processor

et al. 2021

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Simple tuneup of fast two-qubit gates is essential for the scaling of quantum processors. We introduce the sudden variant (SNZ) of the net zero scheme realizing controlled-Z (CZ) gates by flux control of transmon frequency. SNZ CZ gates realized in a multitransmon processor operate at the speed limit of transverse coupling between computational and noncomputational states by maximizing intermediate leakage. Beyond speed, the key advantage of SNZ is tuneup simplicity, owing to the regular structure of conditional phase and leakage as a function of two control parameters. SNZ is compatible with scalable schemes for quantum error correction and adaptable to generalized conditional-phase gates useful in intermediate-scale applications.

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Implementation of Conditional Phase Gates Based on Tunable ZZ Interactions

Cited by 126 publications

References 51 publications

Observation of a Floquet symmetry-protected topological phase with superconducting qubits

Observation of a Floquet symmetry-protected topological phase with superconducting qubits

Topological Photonics on Superconducting Quantum Circuits with Parametric Couplings

High-Fidelity Controlled- Z Gate with Maximal Intermediate Leakage Operating at the Speed Limit in a Superconducting Quantum Processor

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