Detecting Single Microwave Photons with NV Centers in Diamond

At a Glance

Metadata	Details
Publication Date	2023-04-21
Journal	Materials
Authors	Olivia Woodman, Abdolreza Pasharavesh, C. M. Wilson, Michal Bajcsy
Institutions	University of Waterloo
Citations	1
Analysis	Full AI Review Included

Technical Documentation & Analysis: Single Microwave Photon Detection in Diamond

This document analyzes the research paper “Detecting Single Microwave Photons with NV Centers in Diamond” (Woodman et al., 2023) and outlines how 6CCVD’s advanced MPCVD diamond materials and fabrication services are essential for the successful realization and scaling of this quantum technology.

Executive Summary

This research proposes a highly efficient, solid-state scheme for detecting single microwave photons, leveraging the unique quantum properties of Nitrogen-Vacancy (NV^-) centers in diamond.

Core Mechanism: Detection relies on Dipole-Induced Transparency (DIT) to optically read out the spin state of an NV^- center, which is controlled by the presence of a microwave photon.
Material Platform: The system requires high-purity Single Crystal Diamond (SCD) hosting NV^- defects coupled simultaneously to a high-Q optical cavity (e.g., Fabry-Perot or Nanobeam) and a microwave cavity (e.g., Coplanar Waveguide, CPW).
Performance Metrics: Numerical simulations predict high performance, achieving detection efficiencies approaching 90% and fidelities exceeding 90% under realistic cavity parameters (Q-factors up to 10⁶).
Key Challenge: Achieving the required strong coupling ($g_b / 2\pi \approx 10$ kHz) between the NV electronic spin and the microwave cavity field, often requiring precise integration of diamond with superconducting circuits (CPW).
6CCVD Value Proposition: 6CCVD provides the necessary foundation—ultra-low strain, high-purity SCD substrates, custom dimensions for integration into CPW circuits, and in-house metalization capabilities (Ti/Au) critical for fabricating the superconducting microwave cavity components.

Technical Specifications

The following parameters were extracted from the simulation results and literature review, representing the target specifications for the NV center and coupled cavities necessary for high-fidelity detection.

Parameter	Value	Unit	Context
Target Detection Efficiency	> 90	%	Achievable with optimized parameters.
Target Fidelity	> 90	%	Achievable with optimized parameters.
NV Zero-Field Splitting	2.87	GHz	Separation between $m_s = \pm 1$ and $m_s = 0$ states.
Optical Transition ($\omega_{dg}$)	$2\pi \times 470$	THz	Resonance frequency for the optical cavity probe.
Microwave Transition ($\omega_{sg}$)	$2\pi \times 3.4$	GHz	Resonance frequency for the spin flip ($
Target Optical Q-Factor ($Q_a$)	$10^6$	Dimensionless	Used in simulations for high cooperativity ($\eta = 0.4$).
Target Microwave Q-Factor ($Q_b$)	$10^6$	Dimensionless	Used in simulations for high efficiency.
Required Microwave Coupling ($g_b / 2\pi$)	10	kHz	Minimum coupling strength for 90% fidelity (Figure 7).
NV Longitudinal Lifetime ($\tau$)	11.9	ns	Used in cooperativity calculation.
*NV Coherence Lifetime ($\tau^$)**	5.8	ns	Used in cooperativity calculation.
NV (s) State Decay ($\Gamma_s / 2\pi$)	21.2	Hz	Metastable singlet state decay rate.
Debye-Waller Factor ($\epsilon$)	0.03	Dimensionless	Ratio of ZPL emission to total emission.

Key Methodologies

The proposed single microwave photon detector relies on a hybrid solid-state quantum system and advanced simulation techniques to validate performance.

NV Center Integration: The scheme utilizes the negatively charged Nitrogen-Vacancy (NV^-) defect in the diamond lattice, selected for its long coherence times and all-optical spin initialization and readout capabilities.
Dual Cavity Coupling: The NV center is simultaneously coupled to two distinct resonant cavities:
- An Optical Cavity (e.g., Fabry-Perot, Nanobeam) coupled to the spin-selective $|g\rangle \leftrightarrow |d\rangle$ transition for readout.
- A Microwave Cavity (e.g., Coplanar Waveguide, CPW) coupled to the electronic spin transition $|g\rangle \leftrightarrow |s\rangle$ for control.
Dipole-Induced Transparency (DIT): The presence of a microwave photon switches the NV spin state from $|g\rangle$ to $|s\rangle$. This spin change alters the optical cavity’s transmissivity (DIT effect), allowing the microwave photon’s presence to be inferred by measuring the transmitted optical photons.
Performance Modeling: The system dynamics were modeled using a Lindblad master equation, solved via both direct numerical integration and the Monte Carlo Wave Function (MCWF) quantum trajectory approach, accounting for realistic cavity decay rates and imperfect optical detector efficiency (down to 75%).
Ensemble Scaling: The paper suggests using an ensemble of N NV centers to enhance the effective cooperativity ($\eta_{eff} = N\eta$) and effective coupling constant ($g_{eff} = \sqrt{N}g_b$), improving population transfer and system robustness.

6CCVD Solutions & Capabilities

The successful realization of this high-performance quantum detector hinges on the quality and precise engineering of the diamond substrate and its integration with high-Q cavities. 6CCVD is uniquely positioned to supply the foundational materials and fabrication services required to replicate and scale this research.

Applicable Materials

To achieve the long coherence times and high optical quality required for NV center quantum applications, the highest grade of diamond is necessary.

Research Requirement	6CCVD Material Solution	Key Benefit for Application
High-Purity Substrate	Optical Grade Single Crystal Diamond (SCD)	Ultra-low strain, extremely low nitrogen content (< 1 ppb) necessary for long NV coherence times ($\tau^*$).
Controlled NV Generation	Custom SCD with Controlled Doping	Substrates can be tailored for post-growth ion implantation or in-situ growth techniques to achieve optimal NV density (single NV or controlled ensembles).
Cavity Integration	Polycrystalline Diamond (PCD) Substrates	Available in large formats (up to 125mm) for scalable fabrication of integrated photonic crystal cavities (PCCs) or nanobeams.
Quantum Sensing (Future Extension)	Boron-Doped Diamond (BDD)	While not used in this specific DIT scheme, BDD is available for related quantum sensing or electrochemical applications requiring conductive diamond.

Customization Potential

The proposed detector relies heavily on integrating the diamond platform with external superconducting circuits (CPW) and high-Q optical structures. 6CCVD offers critical in-house services to facilitate this integration:

Custom Dimensions and Thickness:
- We provide SCD plates and wafers in custom sizes necessary for integration into specific CPW geometries.
- Thickness control is available from 0.1 µm up to 500 µm for active layers, and substrates up to 10 mm for robust mechanical support.
Ultra-Smooth Polishing:
- Achieving high Q-factors in optical cavities (up to $10^6$) requires extremely smooth surfaces to minimize scattering losses.
- 6CCVD guarantees surface roughness Ra < 1 nm for SCD and Ra < 5 nm for inch-size PCD, ideal for fabricating high-performance photonic crystal structures.
In-House Metalization for CPW:
- The microwave cavity (CPW) often requires superconducting or high-conductivity metal layers (e.g., Ti/Au or Nb).
- 6CCVD offers internal metalization services, including Au, Pt, Pd, Ti, W, and Cu, allowing researchers to deposit the necessary contact and waveguide layers directly onto the diamond substrate with high precision.

Engineering Support

6CCVD’s in-house PhD team specializes in the material science of diamond for quantum applications. We offer consultation services to optimize material selection and processing parameters for similar Microwave-to-Optical Transduction and Quantum Sensing projects. Our expertise ensures that the starting material meets the stringent requirements for low decoherence and high coupling efficiency demonstrated in this paper.

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

View Original Abstract

We propose a scheme for detecting single microwave photons using dipole-induced transparency (DIT) in an optical cavity resonantly coupled to a spin-selective transition of a negatively charged nitrogen-vacancy (NV−) defect in diamond crystal lattices. In this scheme, the microwave photons control the interaction of the optical cavity with the NV− center by addressing the spin state of the defect. The spin, in turn, is measured with high fidelity by counting the number of reflected photons when the cavity is probed by resonant laser light. To evaluate the performance of the proposed scheme, we derive the governing master equation and solve it through both direct integration and the Monte Carlo approach. Using these numerical simulations, we then investigate the effects of different parameters on the detection performance and find their corresponding optimized values. Our results indicate that detection efficiencies approaching 90% and fidelities exceeding 90% could be achieved when using realistic optical and microwave cavity parameters.

Tech Support

Original Source

DOI: https://doi.org/10.3390/ma16083274

References

2012 - Single-photon spectroscopy of a single molecule [Crossref]
2007 - Quantum key distribution over a 40-dB channel loss using superconducting single-photon detectors [Crossref]
2017 - Microwave photonics with superconducting quantum circuits [Crossref]
2020 - Hybrid quantum systems with circuit quantum electrodynamics [Crossref]
2022 - Towards a microwave single-photon counter for searching axions [Crossref]
2015 - Microwave quantum illumination [Crossref]
2020 - Microwave photon detection by an Al Josephson junction [Crossref]
2014 - Quantum nondemolition detection of a propagating microwave photon [Crossref]
2016 - Single microwave-photon detector using an artificial Λ-type three-level system [Crossref]