Control and single-shot readout of an ion embedded in a nanophotonic cavity
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2020-03-30 |
| Journal | Nature |
| Authors | Jonathan M. Kindem, Andrei Ruskuc, John G. Bartholomew, Jake Rochman, Yan Qi Huan |
| Institutions | California Institute of Technology, Kavli Energy NanoScience Institute |
| Citations | 221 |
| Analysis | Full AI Review Included |
Executive Summary
Section titled âExecutive Summaryâ- Platform Validation: Demonstrated coherent control and high-fidelity single-shot readout (95.3%) of a single 171Yb3+ ion spin qubit embedded in a Yttrium Orthovanadate (YVO) nanophotonic cavity.
- Exceptional Spin Coherence: Achieved spin coherence times (T2,s) up to 30 ms using dynamical decoupling (CPMG), approaching the measured qubit lifetime (T1) of 54 ms.
- Temperature Robustness: Spin coherence and lifetime were preserved at temperatures up to 1.2 K, making the platform viable for economical 4He cryogenics.
- First-Order Insensitivity: The chosen |0>g <-> |1>g qubit transition is first-order insensitive to magnetic field fluctuations (ZEFOZ transition), crucial for long coherence.
- Cavity Enhancement: Purcell-enhanced optical emission (factor of 117) facilitates efficient spin initialization and conditional single-shot readout, boosting the optical transition cyclicity (Beta|| > 99.6%).
- Quantum Network Readiness: The measured coherence time is equivalent to light propagation over thousands of kilometers in optical fiber, showcasing a solid-state platform for the future quantum internet.
Technical Specifications
Section titled âTechnical Specificationsâ| Parameter | Value | Unit | Context |
|---|---|---|---|
| Qubit Spin Coherence (T2,s) | 30 | ms | Maximum achieved using CPMG sequence |
| Qubit Lifetime (T1) | 54 | ms | Measured at 40 mK |
| Single-Shot Readout Fidelity | 95.3 | % | Average fidelity using conditional dual readout |
| Optical Lifetime (Cavity) | 2.27 | ”s | Ion X, reduced from bulk lifetime |
| Optical Lifetime (Bulk) | 267 | ”s | Bulk YVO reference |
| Effective Purcell Factor (η) | 117 | Dimensionless | Enhancement of emission rate |
| Single-Photon Coupling Rate (g) | 2pi x 23 | MHz | Calculated coupling rate |
| Cavity Quality Factor (Q) | 1 x 104 | Dimensionless | Photonic crystal cavity |
| Cavity Mode Volume (V) | 0.095 | ”m3 | ~1(lambda/nYVO)3 |
| Spin Qubit Transition Frequency | ~675 | MHz | Zero applied magnetic field |
| Operating Temperature Range | 40 mK to 1.2 | K | Coherence preserved across this range |
| 171Yb3+ Concentration | ~20 | ppb | Residual concentration in YVO host |
| Optical Linewidth (Integrated) | 1.4 | MHz | FWHM, long-term spectral stability |
Key Methodologies
Section titled âKey Methodologiesâ- Nanophotonic Fabrication: Photonic crystal cavities were fabricated directly into the YVO host crystal using Focused-Ion-Beam (FIB) milling to create a triangular nanobeam structure.
- Material System: YVO crystal containing residual 171Yb3+ ions (~20 ppb concentration) was used. The D2d site symmetry of Y3+ substitution minimizes sensitivity to electric field fluctuations.
- Cryogenic Setup: The device was mounted on the mixing chamber plate of a dilution refrigerator, operating at a base temperature of 40 mK.
- Cavity Resonance Tuning: Fine tuning of the cavity resonance to the ion transition was achieved by controlled deposition and sublimation of frozen nitrogen (N2) gas onto the device surface.
- Optical Addressing: Two frequency-stabilized continuous-wave lasers (Ti:Sapphire and ECDL) were used, modulated by acousto-optic modulators (AOMs) to generate precise optical pulses for excitation and readout.
- Spin Manipulation: Microwave (MW) control pulses were delivered via a coplanar waveguide (CPW) adjacent to the cavity, enabling fast and efficient manipulation of the 675 MHz spin qubit transition.
- Coherence Protection: Dynamical decoupling sequences (Carr-Purcell-Meiboom-Gill, CPMG, and XY-8) were applied to suppress quasi-static magnetic noise from the nuclear spin bath, extending T2,s to 30 ms.
- Spin Initialization: The ion was initialized into the |0>g state using optical and microwave pumping sequences on transitions F, A, and fe, followed by cavity-enhanced decay via transition E.
- Conditional Single-Shot Readout (SSRO): A dual readout scheme was employed, consisting of two consecutive optical read periods on transition A separated by a MW pi pulse. The state assignment was conditioned on detecting 01 or 10 photon counts across the two reads to ensure the ion remained in the qubit subspace.
Commercial Applications
Section titled âCommercial Applicationsâ- Quantum Networking Infrastructure: The long spin coherence times (30 ms) are essential for developing quantum repeaters and nodes capable of distributing entanglement over intercity distances.
- Solid-State Quantum Memories: The 171Yb3+:YVO platform is a strong candidate for high-performance quantum memories (Ref 24) required for buffering and synchronizing photon traffic in complex quantum networks.
- Hybrid Quantum Transduction: The systemâs optical and spin properties point toward its use as a quantum transducer (Ref 25), coupling optical photons to microwave-frequency qubits (like superconducting circuits).
- High-Fidelity Qubit Systems: The demonstrated 95.3% single-shot readout fidelity is a critical metric for scalable quantum computing architectures that require error correction.
- Advanced Material Characterization: The techniques used (PLE, ODMR, dynamical decoupling) are directly applicable to characterizing defects and rare-earth dopants in other advanced crystalline materials (e.g., diamond, silicon carbide) for quantum sensing applications.