| Metadata | Details |
|---|
| Publication Date | 2020-07-10 |
| Journal | Physical Review Letters |
| Authors | Wentao Ji, Lin Zhang, Mengqi Wang, Long Zhang, Yuhang Guo |
| Institutions | Hefei National Center for Physical Sciences at Nanoscale, University of Chinese Academy of Sciences |
| Citations | 54 |
| Analysis | Full AI Review Included |
- Core Achievement: Demonstrated a complete quantum simulation of a novel, previously unrealized three-dimensional (3D) chiral topological insulator (TI) using a solid-state Nitrogen-Vacancy (NV) center in diamond.
- Methodological Breakthrough: Successfully implemented the Dynamical Bulk-Surface Correspondence (DBSC) in momentum space, which links the bulk topology of the 3D phase to measurable quench dynamics emerging on 2D Band Inversion Surfaces (BISs).
- Symmetry Validation: Experimentally verified the chiral symmetry protection of the phase by measuring dynamical spin textures on BISs, observing perfect (broken) topology when the chiral symmetry was preserved (broken).
- Topological Characterization: Directly measured the bulk topology by characterizing topological charges enclosed by the BISs, confirming the 3D winding number (v3 = +1 in the measured phase).
- Emergent Dynamics: Identified an emergent Dynamical Topological Transition (DTT) when varying the quench depth, with a measured critical value mc â 2.7to, corresponding to the movement of topological charges across the BIS.
- Platform Robustness: The NV center simulator operates at room temperature and utilizes momentum space engineering, offering a robust and accessible avenue for exploring high-dimensional topological phases beyond the limits of conventional condensed matter systems.
| Parameter | Value | Unit | Context |
|---|
| Simulator Platform | Nitrogen-Vacancy (NV) Center | N/A | Solid-state spin system in diamond. |
| Operating Temperature | Room Temperature | N/A | Experiment performed on a home-built confocal setup. |
| Diamond Orientation | [111] | N/A | NV center orientation used with solid immersion lens. |
| Electron Zero-Field Splitting (D) | 2.87 | GHz | Intrinsic property of the NV center. |
| Nuclear Quadrupolar Interaction (Q) | -4.95 | MHz | Intrinsic property of the 14N nuclear spin. |
| Hyperfine Interaction (A) | -2.16 | MHz | Coupling between electron and nuclear spins. |
| Applied Magnetic Field | 514 | G | Applied along the NV symmetry axis. |
| Electron Zeeman Splitting (Ďe) | 1439 | MHz | Resulting splitting under the applied magnetic field. |
| Nuclear Zeeman Splitting (Ďn) | 154 | kHz | Resulting splitting under the applied magnetic field. |
| Qubit Subspace | {ms = 0, -1} â {mi = +1, 0} | N/A | Two-qubit system (electron and 14N nuclear spin). |
| Spin-Orbit Coupling (tso) | 0.2to | N/A | Example parameter used in the H3D simulation. |
| Critical Quench Depth (mc) | 2.7to (Experimental) | N/A | Point of the emergent Dynamical Topological Transition. |
| BIS Measurement Step Size | 0.1Ď | N/A | Mesh grid step size for kx, ky, kz in Brillouin zone. |
| g(k) Field Sampling Step | 0.02Ď | N/A | Sampling step across the BIS along the norm direction. |
- NV Center Setup and Control: A two-qubit system was established using the electron spin (S=1) and the intrinsic 14N nuclear spin (I=1) of a [111] oriented NV center. Control was achieved using microwave (MW) and radio-frequency (RF) pulses generated by an arbitrary wave generator.
- Hamiltonian Emulation: The 3D chiral topological insulator Hamiltonian (H3D) was mapped onto the effective NV Hamiltonian (Heff) by relating the Bloch momentum (k) to the control parameters (magnetic field, MW frequency, and RF rotation angle).
- Quantum Quench Protocol: The experiment followed a three-step quantum circuit:
- Initialization: The system was initialized to the |00> state (an eigenstate of the pre-quench Hamiltonian) using a green laser pulse, followed by unitary control to polarize the state along the desired quench axis (Yi).
- Evolution: The state evolved under the simulated H3D for a time t, corresponding to the post-quench dynamics.
- Readout: The spin polarization (â¨Yj(t)âŠ) was measured by transforming the component of interest to the z-basis, followed by photoluminescence (PL) photon counting.
- Dynamical Bulk-Surface Correspondence (DBSC) Implementation:
- BIS Identification: The 2D Band Inversion Surfaces (BISs) were identified as the momentum points where the time-averaged spin polarizations (â¨Yi(k)âŠ) vanish.
- Spin Texture Measurement: The emergent dynamical spin-texture field g(k) was measured on the reconstructed BIS mesh by sampling spin polarizations along the direction normal to the BIS.
- Topological Charge Measurement: To characterize the bulk topology, a series of quenches along different axes (Yi) were performed, measuring the time-averaged spin polarization â¨Y0(k)âŠi. This data was used to construct the dynamical field Î(k), whose winding number characterizes the bulk topological charge.
- Symmetry Breaking Study: Chiral symmetry breaking was simulated by introducing an additional term (h4Îł4) into H3D via an extra rotation of the nuclear spin, allowing measurement of the resulting non-quantized invariant (WSB).
- Robustness Testing: The measurements were validated against spin dephasing by extending the evolution time and confirming that the time-averaged spin polarization remained consistent, demonstrating the robustness of the dynamical characterization methods.
- Quantum Computing and Simulation:
- NV centers are a leading platform for solid-state quantum computation. This work demonstrates the ability to simulate complex, high-dimensional Hamiltonians, which is critical for developing scalable quantum algorithms and hardware architectures.
- Topological Quantum Materials Research:
- The DBSC methodology provides a powerful, boundary-free technique for characterizing topological invariants. This accelerates the discovery and verification of new topological phases (e.g., 4D or 5D systems) that are inaccessible in natural condensed matter.
- Advanced Quantum Sensing:
- The precise MW and RF control techniques developed for spin manipulation are directly applicable to enhancing the sensitivity and coherence of NV-based quantum sensors (e.g., magnetometers, thermometers).
- CVD Diamond Manufacturing (6ccvd.com relevance):
- High-fidelity quantum experiments require ultra-pure, defect-controlled diamond substrates, often grown via Chemical Vapor Deposition (CVD). The use of specific crystal orientations (e.g., [111]) and controlled NV creation techniques drives demand for specialized, high-quality CVD diamond materials.
- High-Frequency Quantum Control Systems:
- The reliance on arbitrary wave generators for precise, multi-frequency MW and RF pulsing demonstrates expertise in high-speed, low-noise quantum control electronics necessary for operating large-scale qubit arrays.
View Original Abstract
Quantum simulation, as a state-of-the-art technique, provides a powerful way to explore topological quantum phases beyond natural limits. Nevertheless, it is usually hard to simulate both the bulk and surface topological physics at the same time to reveal their correspondence. Here we build up a quantum simulator using nitrogen-vacancy center to investigate a three-dimensional (3D) chiral topological insulator, and demonstrate the study of both the bulk and surface topological physics by quantum quenches. First, a dynamical bulk-surface correspondence in momentum space is observed, showing that the bulk topology of the 3D phase uniquely corresponds to the nontrivial quench dynamics emerging on 2D momentum hypersurfaces called band inversion surfaces (BISs). This is the momentum-space counterpart of the bulk-boundary correspondence in real space. Further, the symmetry protection of the 3D chiral phase is uncovered by measuring dynamical spin textures on BISs, which exhibit perfect (broken) topology when the chiral symmetry is preserved (broken). Finally, we measure the topological charges to characterize directly the bulk topology and identify an emergent dynamical topological transition when varying the quenches from deep to shallow regimes. This work demonstrates how a full study of topological phases can be achieved in quantum simulators.