Applications of Diamond in Quantum Technology

Fundamental Principles

High-purity single-crystal CVD diamond can be precisely engineered with color centers (point defects) including nitrogen-vacancy (NV), silicon-vacancy (SiV), tin-vacancy (SnV), and germanium-vacancy (GeV) centers.

The electron spins of these color centers serve as solid-state quantum bits (qubits) with unique advantages:

1.Long spin coherence time at room temperature, eliminating the need for cryogenic cooling (unlike superconducting and trapped-ion systems).

2.Ultra-wide bandgap, high electrical insulation, ultra-high thermal conductivity, radiation hardness, and thermal expansion coefficient (CTE ≈ 1.1 ppm/K).

3.Optical initialization, microwave spin manipulation, and photonic quantum-state readout, enabling spin-photon coupling interfaces.

4.MPCVD growth allows precise control of defect concentration and color center array positioning, compatible with semiconductor micro-nano fabrication.

1. Quantum Computing: Diamond Spin Qubits and Quantum Chips

1.1 NV Center Qubits (Mainstream for Mass Production Verification)

• Structure: One nitrogen atom plus an adjacent lattice vacancy, with triplet spin S=1, enabling stable room-temperature quantum information storage.

• Performance: Microsecond-scale coherence time at room temperature, up to 10 ms at low temperatures; logic gate fidelity meets fault-tolerant quantum computing thresholds.

• Device format: High-purity quantum-grade single-crystal diamond substrates with patterned NV center arrays fabricated via ion implantation and annealing, forming multi-qubit quantum registers.

• Applications:

• General-purpose solid-state quantum computing prototypes

• Quantum simulation of topological materials, molecular energy levels, and long-range spin interactions

• Quantum error correction and quantum AI algorithm validation

1.2 Group-IV Color Centers (SiV/SnV/GeV) for Quantum Networks

• Advantages: Ultra-narrow linewidth, telecom C-band photon emission, and much higher spin-photon coupling efficiency than NV centers.

• Applications: Distributed quantum computing nodes, remote qubit entanglement, quantum repeater chips.

• Technology: Femtosecond laser direct writing of individual color centers for precise micron-scale positioning in integrated quantum photonic wafers.

1.3 Diamond Quantum Chip Substrates and Carriers

High-thermal-conductivity single-crystal diamond (same grade used in AI supercomputing liquid cooling) suppresses thermal drift in multi-qubit microwave circuits.

Integrated microchannel cold plates combined with diamond quantum substrates achieve temperature fluctuations <0.1°C under long-term full load, greatly improving quantum gate stability.

2. Quantum Communication: Single-Photon Sources, Quantum Memory, Quantum Repeaters

2.1 Deterministic Single-Photon Sources (Core for Quantum Encryption)

SiV/SnV centers embedded in diamond nanocavities or waveguides generate high-purity single photons on demand with negligible multi-photon noise.

Compared with attenuated lasers, they improve QKD key generation rates by two orders of magnitude, suitable for metropolitan and satellite-ground quantum encryption.

2.2 Room-Temperature Solid-State Quantum Memory

NV center spins store photonic quantum states at room temperature without cryogenic systems, enabling compact quantum repeaters.

Solves fiber loss and entanglement decay in long-distance quantum communication, supporting multi-node terrestrial quantum backbone networks.

2.3 Spin-Photon Coupling Interface Chips

Diamond-integrated waveguides and optical resonators enable efficient conversion between spin qubits and communication photons, connecting independent quantum computing nodes to build a distributed quantum internet.

3. Quantum Precision Sensing (Most Mature Industrial Sector)

Diamond quantum sensors exhibit extreme sensitivity to magnetic fields, temperature, electric fields, and stress, with four core strengths:

room-temperature operation, nanoscale spatial resolution, ultra-high sensitivity, label-free detection.

3.1 High-Sensitivity Magnetometry

• Sensitivity: nT–pT/√Hz, spatial resolution <100 nm.

• Power grid: diamond quantum current transformers deployed on 110 kV grids with 0.05% accuracy over 0–1000 A, immune to thermal drift and ferromagnetic saturation.

• Inertial navigation: geomagnetic quantum compasses for underground and underwater navigation without satellite signals.

• Aerospace NDI: imaging of micro-defects in aircraft composites and engine turbines.

3.2 Biomedical Nano Quantum Microscopy

Shallow-implanted NV diamond probes enable label-free mapping of intracellular magnetic fields and local temperature in living cells.

Supports single-molecule NMR and magnetoencephalography (MEG) with resolution 1000× higher than conventional MRI.

3.3 High-Resolution Quantum Thermometry

Single-crystal diamond thin films enable real-time microscale temperature measurement on high-power quantum chips and superconducting circuits, supporting thermal characterization for quantum processors and AI liquid cooling systems.

3.4 Electric Field and Strain Sensing

Scanning of internal electric field distribution in semiconductor wafers and strain analysis in power device packaging for quantum chip and third-generation semiconductor process control.

3.5 Quantum Mineral Exploration

Portable diamond quantum magnetometers detect geomagnetic anomalies for underground ore and hydrocarbon reservoirs, with robust performance in extreme field environments.

3.6 Quantum Metrology Standards

Room-temperature portable primary standards for magnetic field and temperature calibration, replacing bulky superconducting SQUID systems in national metrology institutes.

4. Integrated Quantum Photonics: Diamond Photonic Chips and Micro-Optical Components

Diamond features ultra-wide transparency (UV–visible–NIR), high laser damage threshold, and low optical loss, making it an ideal quantum photonic platform:

1.Single-crystal diamond waveguides, photonic crystals, and microdisk resonators for integrated on-chip quantum optical circuits.

2.Monolithic integration of quantum interferometers, beam splitters, and single-photon filters.

3.High-power quantum laser windows and VUV optical components resistant to high-energy photon radiation.

4.Heterogeneous bonding of diamond photonic chips with silicon photonic wafers for large-scale on-chip quantum signal processing.

5. Quantum Devices for Extreme Environments

Diamond operates stably from −270°C to 700°C, with exceptional radiation hardness and corrosion resistance:

• Satellite-borne quantum communication payloads: single-photon sources and on-board quantum memory stable under cosmic radiation.

• In-core quantum detection: remote magnetic field and temperature monitoring in nuclear reactors.

• Quantum diagnostic components for high-power particle accelerators.

6. Quantum-Grade Diamond Material Classification

6.1 High-Purity Single-Crystal CVD Diamond

PPB-level impurity control, low dislocation density, 2–4 inch wafers for quantum qubits, single-photon sources, and high-precision quantum probes.

6.2 Ultra-Thin Quantum-Grade Diamond Films

Thickness 50 nm–20 μm, heteroepitaxial MPCVD growth, suitable for microfluidic cooling integration and on-chip optoelectronic packaging.

6.3 Diamond-Copper / Diamond-Aluminum Composite Heat Spreader Substrates

High-thermal-conductivity composites for microchannel cold plates in quantum computing racks, compatible with single-phase, immersion, and two-phase liquid cooling.

6.4 Polycrystalline Optical Diamond

Cost-effective large-area windows and lenses for high-power quantum laser systems.