State Readout of a Trapped Ion Qubit Using a Trap-Integrated Superconducting Photon Detector

Abstract

We report high-fidelity state readout of a trapped ion qubit using a trap-integrated photon detector. We determine the hyperfine qubit state of a single 9 Be + ion held in a surface-electrode rf ion trap by counting state-dependent ion fluorescence photons with a superconducting nanowire single-photon detector fabricated into the trap structure. The average readout fidelity is 0.9991(1), with a mean readout duration of 46 µs, and is limited by the polarization impurity of the readout laser beam and by off-resonant optical pumping. Because there are no intervening optical elements between the ion and the detector, we can use the ion fluorescence as a self-calibrated photon source to determine the detector quantum efficiency and its dependence on photon incidence angle and polarization.

TSV-integrated surface electrode ion trap for scalable quantum information processing

“…Taking advantage of wellestablished microfabrication techniques (i.e., MEMS and CMOS), surface electrode ion traps exhibits flexible design, reproducible fabrication and mass production 3 . More importantly, the possible integration with photonics components (i.e., waveguide, grating coupler [4][5][6] and photodetector 7 ) enables precise control and measurement on individual trapped ion. These features make surface electrode ion trap highly promising for large scale QIP.…”

Quantum computing hardware in the cloud: Should a computational chemist care?

“…For qubits without direct state selectivity of the fluorescence laser, the dark state is transferred into a 'shelf' state that does not couple to the fluorescence laser and the excited state. Ionposition resolved fluorescence can be detected with arrays of photomultiplier tubes or avalanche photodiodes, on an electron-multiplying charge coupled device camera [67], or with superconducting nanowire single-photon detectors integrated into the trap chip [68]. Fluorescence can be collected over a fixed time-bin and analysed with threshold or maximum likelihood algorithms, or with real-time analysis and adaptive readout duration.…”

“…Fluorescence can be collected over a fixed time-bin and analysed with threshold or maximum likelihood algorithms, or with real-time analysis and adaptive readout duration. With sufficiently low background counts and high photon collection and detection efficiency, real-time analysis achieves the same fidelities as fixed-time threshold analysis, but is considerably faster [68,69].…”

“…Coherence times in trapped ions are T * 2 = 50 s on magnetic-field insensitive clock qubits [53] and reach over an hour by employing dynamical decoupling sequences [56]. State-preparation and measurement errors are ε < 1 • 10 −3 , with a mean duration of 46 µs [67][68][69], where ε ≡ 1 − F 100 for fidelity F. Single qubit gates have been performed with errors ε = 1.0(3) • 10 −6 for an rf π/2-pulse of 12 µs pulse duration on a single ion [53]. Fast single qubit gates can be implemented with a pulsed laser trading off fidelity against speed, achieving ε = 7 • 10 −3 for t π/2 = 40 ps [81].…”

Materials Challenges for Trapped-Ion Quantum Computers

“…One very promising path forward is via integration of classical control and measurement technology into the ion traps themselves 43,50 . As chip-scale ion traps are fast becoming a standard trap technology in the field, it is an opportune time to consider on-chip integration technologies such as photonic integrated circuits (PICs) for delivery of light 54 , complementary metal-oxide-semiconductor (CMOS) integrated circuits (ICs) 55 for electric and magnetic-field control and electronic signal processsing, and on-chip single-photon detectors for qubit state readout 26 .…”