Skip to content
6CCVD Research

Efficient Implementation of a Quantum Algorithm in a Single Nitrogen-Vacancy Center of Diamond

At a Glance

Section titled “At a Glance”
MetadataDetails
Publication Date2020-07-14
JournalPhysical Review Letters
AuthorsJingfu Zhang, Swathi S. Hegde, Dieter Suter
InstitutionsTU Dortmund University
Citations54
AnalysisFull AI Review Included

Technical Documentation & Analysis: Efficient Quantum Computing in NV Diamond

Section titled “Technical Documentation & Analysis: Efficient Quantum Computing in NV Diamond”

This document analyzes the research paper “Efficient Implementation of a Quantum Algorithm in a Single Nitrogen Vacancy Center of Diamond” and connects the experimental requirements to the advanced material solutions offered by 6CCVD.

Executive Summary

Section titled “Executive Summary”

The research successfully demonstrates the efficient implementation of Grover’s quantum search algorithm using a hybrid 2-qubit system based on a single Nitrogen Vacancy (NV) center in diamond.

  • Core Achievement: Implementation of Grover’s search using the NV electron spin (Qubit 1) coupled to a 13C nuclear spin (Qubit 2).
  • Efficiency Breakthrough: The entire quantum search was implemented using highly efficient indirect control via only 4 optimized Microwave (MW) pulses, significantly reducing the control cost compared to traditional radio-frequency (RF) methods.
  • Performance Metrics: Experimental target state populations ranged from 0.76 ± 0.03 to 0.87 ± 0.05, substantially exceeding the classical search probability of 0.25.
  • Material Requirement: Success hinges on the use of ultra-pure, isotopically enriched diamond (99.995% 12C, < 10 ppb N) to maximize the electron spin coherence time (T2* ~35 ”s).
  • Limitation & Solution: The primary source of infidelity is decoherence during the pulse sequence (duration ~13 ”s). Further improvements require increasing the electron spin coherence time, necessitating even lower substitutional nitrogen concentrations.
  • Scalability Demonstrated: Numerical simulations confirm the scalability of the Optimal Control (OC) scheme, achieving high gate fidelities (> 0.930) for controlled-Rz(π) gates in systems up to 5 qubits (electron + 4 13C spins).

Technical Specifications

Section titled “Technical Specifications”

The following hard data points were extracted from the experimental setup and results:

ParameterValueUnitContext
Diamond Isotopic Purity99.995%12CUsed to minimize decoherence.
Substitutional Nitrogen Concentration< 10ppbUltra-low concentration required for long T2*.
Static Magnetic Field (B)14.8mTApplied along the NV symmetry axis (z-axis).
Zero-Field Splitting (D)2.87GHzElectron spin property.
13C Axial Hyperfine Coupling (Azz)-0.152MHzUsed in the Hamiltonian for control optimization.
13C Transverse Hyperfine Coupling (Azx)0.110MHzUsed in the Hamiltonian for control optimization.
MW Rabi Frequency (w1/2π)0.5MHzNominal frequency used for pulse optimization.
Initial State Fidelity (Fini)0.92 ± 0.01N/AMeasured via quantum state tomography.
Final State Fidelity (F|11>)0.85 ± 0.03N/AMeasured after the complete Grover’s search.
Electron Spin Decoherence Time (T2*)~35”sMeasured from ESR Free Induction Decay (FID).
Quantum Search Duration12.989”sTotal duration of the 4-pulse sequence for target
Simulated Gate Fidelity (5 Qubits)> 0.930N/AControlled-Rz(π) gate simulation results.

Key Methodologies

Section titled “Key Methodologies”

The experiment relied on precise material selection and advanced quantum control techniques:

  1. Material Selection: Used ultra-pure, isotopically enriched Single Crystal Diamond (SCD) with 99.995% 12C and substitutional nitrogen concentration below 10 ppb to minimize environmental noise and maximize coherence.
  2. Optical Initialization: The electron spin was initialized into the ms = 0 state using a 4 ”s, 0.5 mW, 532 nm continuous wave laser pulse delivered via a confocal microscope setup.
  3. Qubit Definition: The 2-qubit system was defined by the electron spin subspace {|0>, |-1>} (Qubit 1) and the 13C nuclear spin {|↑>, |↓>} (Qubit 2).
  4. Indirect Control Implementation: Quantum gates were implemented using only Microwave (MW) pulses applied to the electron spin, leveraging the anisotropic hyperfine interaction and free precession to indirectly control the nuclear spin.
  5. Optimal Control (OC) Optimization: Pulse sequences (4 MW pulses, 5 delays) were optimized using Optimal Control theory and a genetic algorithm to maximize the overlap (fidelity) between the generated operation and the required quantum circuit.
  6. Robustness Engineering: Pulse sequences were specifically optimized for robustness against fluctuations in the MW Rabi frequency (w1/2π) across the range [0.48, 0.52] MHz, ensuring experimental stability over time.

6CCVD Solutions & Capabilities

Section titled “6CCVD Solutions & Capabilities”

The successful replication and extension of this high-efficiency quantum computing research require diamond materials with exceptional purity, isotopic control, and surface quality. 6CCVD is uniquely positioned to supply the necessary components.

Requirement from Research Paper6CCVD Solution & CapabilityTechnical Advantage
Ultra-Low Nitrogen Concentration (Need for < 10 ppb N, ideally lower)Optical Grade Single Crystal Diamond (SCD). We specialize in MPCVD growth of SCD with ultra-low substitutional nitrogen (N) concentration, enabling T2* maximization.Directly addresses the primary source of infidelity (decoherence) by minimizing magnetic noise, allowing researchers to achieve T2* and T2 times significantly longer than the 35 ”s reported.
Isotopic Enrichment (Used 99.995% 12C)Custom Isotopic Control. We offer SCD with isotopic enrichment up to 12C > 99.999% for ultimate spin bath isolation, or controlled introduction of 13C for use as ancillary qubits.Provides the necessary high-purity spin environment while allowing precise control over the density and location of coupled nuclear qubits.
Scalability and Integration (Simulated up to 5 qubits)Large Area SCD/PCD Substrates. We provide custom plates and wafers up to 125mm (PCD) and large-area SCD substrates (up to 10mm thick).Facilitates the transition from single-NV proof-of-concept to integrated, multi-qubit quantum processors and complex microwave delivery structures.
High-Frequency MW Control (Requires precise on-chip delivery)Custom Metalization Services. 6CCVD offers in-house deposition of high-quality thin films (Au, Pt, Pd, Ti, W, Cu) for creating low-loss microwave transmission lines and contact pads directly on the diamond surface.Ensures optimal coupling and minimal signal degradation for the critical MW pulses used in the indirect control scheme, essential for maintaining high gate fidelity.
Optical Access & Stability (Confocal microscope setup)Ultra-Low Roughness Polishing. Our SCD material is polished to achieve surface roughness Ra < 1nm, and inch-size PCD to Ra < 5nm.Guarantees high-efficiency optical initialization (532 nm) and fluorescence collection (637 nm), minimizing scattering losses critical for single-NV experiments.

Engineering Support

Section titled “Engineering Support”

6CCVD’s in-house PhD team can assist researchers and engineers with material selection and optimization for similar NV-based Quantum Computing and Sensing projects. We provide consultation on achieving specific N concentrations, managing strain, and optimizing surface termination to maximize T2 and T2* coherence times.

For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.

View Original Abstract

Quantum computers have the potential to speed up certain problems that are hard for classical computers. Hybrid systems, such as the nitrogen-vacancy (NV) center in diamond, are among the most promising systems to implement quantum computing, provided the control of the different types of qubits can be efficiently implemented. In the case of the NV center, the anisotropic hyperfine interaction allows one to control the nuclear spins indirectly, through gate operations targeting the electron spin, combined with free precession. Here, we demonstrate that this approach allows one to implement a full quantum algorithm, using the example of Grover’s quantum search in a single NV center, whose electron is coupled to a carbon nuclear spin.

Tech Support

Section titled “Tech Support”

Original Source

Section titled “Original Source”

References

Section titled “References”
  1. 2000 - Quantum Computation and Quantum Information
  2. 2008 - Quantum Computing: A Short Course from Theory to Experiment

Reads Similar to This

All-Optical Thermometry with Nitrogen-Vacancy Centers in Nanodiamond-Embedded Polymer Films Phonon-Induced Population Dynamics and Intersystem Crossing in Nitrogen-Vacancy Centers Radiative lifetime of boron-bound excitons in diamond