Silicon Quantum Computing

Technology: Atom Qubits in Silicon

Silicon Quantum Computing (SQC) uses single phosphorus atoms embedded in silicon as qubits. The electron or nuclear spin of the phosphorus atom encodes quantum information.

Key difference from Diraq:

• SQC: Atom qubits (individual atoms placed with atomic precision)
• Diraq: Quantum dots (electron spins in confined regions)

Both are “silicon quantum computing” but different technical approaches.

Atomic Precision Manufacturing

SQC’s breakthrough: Scanning Tunneling Microscope (STM) lithography to place individual phosphorus atoms in silicon with sub-nanometer precision.

Process:

1. Start with ultra-pure silicon
2. Use STM to remove hydrogen atoms in precise pattern
3. Expose to phosphine gas (PH₃)
4. Phosphorus atoms bond at designated positions
5. Encapsulate with more silicon

Result: Qubits positioned with atomic precision (0.1 nanometer accuracy).

Advantage: Identical qubits (every phosphorus atom is the same). No fabrication variation like in quantum dots or superconducting qubits.

Michelle Simmons Leadership

Prof. Michelle Simmons founded SQC after decades at UNSW:

• 2018 Australian of the Year
• Director of ARC Centre of Excellence for Quantum Computation
• Pioneer of atomic-scale device fabrication
• World-leading silicon quantum research (200+ papers)

Academic pedigree: SQC built on 25+ years of UNSW research in silicon quantum computing.

10-Qubit Silicon Processor

SQC demonstrated a 10-qubit silicon quantum processor (2022) with:

• 99.9% gate fidelity (among highest for any qubit modality)
• 30 millisecond coherence times (1,000x longer than superconducting)
• All-to-all connectivity (atoms placed in optimal geometry)

Key metric: Atom qubits have exceptional coherence and fidelity but are currently slower to scale than other approaches.

Australian Government Partnership

SQC is Australia’s flagship quantum company:

• Largest quantum funding in Australia (~$100M+)
• Government strategic partner (quantum sovereignty)
• Telstra investment (national telecom backing quantum)
• CSIRO collaboration (national research organization)

National importance: Australian government views SQC as critical for quantum independence (not relying on US/China quantum technology).

Atomic Precision vs. CMOS Compatibility

SQC approach: Atomic precision, custom fabrication

• Advantage: Perfect qubit uniformity, high fidelity
• Challenge: Slow fabrication (STM lithography is serial process)

Diraq approach: CMOS-compatible quantum dots

• Advantage: Leverage existing fabs, parallel manufacturing
• Challenge: Device variation, lower fidelity (historically)

Strategic difference:

• SQC targets quality first (few perfect qubits)
• Diraq targets scale first (many qubits via standard fabs)

Both are silicon, but different paths to scalable quantum computing.

Competitive Position

vs. Other Silicon Companies (Intel, Diraq):
SQC has academic leadership and government backing. Intel has fab infrastructure. Diraq has CMOS compatibility. Different trade-offs in scaling strategy.

vs. Superconducting (IBM, Google):
SQC: Longer coherence (30 ms vs. 100 μs), higher fidelity (99.9% vs. 99%), but slower scaling (10 qubits vs. 1,000+).

Long-term bet: Silicon qubits with atomic precision will outperform other modalities once manufacturing scales. Coherence and fidelity advantages translate to fewer physical qubits needed for error correction.

Applications (Future)

Once scaled to 100+ qubits:

• Quantum chemistry (molecular simulation)
• Optimization (logistics, finance)
• Cryptography (Shor’s algorithm)
• Machine learning (quantum ML algorithms)

Timeline:

• 2025: 50-qubit processor
• 2027: 100-qubit system with error correction
• 2030: Fault-tolerant quantum computer

Australian Quantum Ecosystem Role

SQC is the centerpiece of Australia’s quantum strategy:

• Largest quantum company by funding
• Most advanced silicon quantum technology
• Government strategic partner
• Academic-industry bridge (UNSW → commercial)

Competitive with:

• Q-CTRL: Software infrastructure (complements SQC hardware)
• Diraq: Alternative silicon approach (competitor but also validates silicon strategy)
• Quantum Brilliance: Diamond qubits (different modality, different applications)

Recent Developments

2024 Milestones:

• Additional funding from Telstra (Australia’s largest telecom)
• CSIRO partnership (quantum manufacturing research)
• Government quantum commercialization program participant
• Expansion of atomic fabrication facilities

Positioning: SQC is transitioning from research lab to commercial quantum computer manufacturer. Target: deliver first commercial silicon quantum computer by late 2020s.

Why SQC Matters

If atomic precision silicon works at scale, SQC could leapfrog other quantum technologies:

Scenario 1: Success

• Silicon qubits with 99.9% fidelity and 30 ms coherence dominate
• Fewer physical qubits needed for error correction (10:1 ratio vs. 1,000:1 for superconducting)
• Australia becomes quantum superpower via SQC technology

Scenario 2: Partial Success

• Atomic precision works but doesn’t scale fast enough
• SQC becomes niche provider of ultra-high-quality qubits
• Hybrid systems (SQC atoms + other modalities)

Scenario 3: Failure

• STM lithography can’t scale to 1,000+ qubits economically
• CMOS-compatible approaches (Diraq, Intel) win silicon quantum computing
• SQC becomes research lab, not commercial quantum company

Current status: SQC has demonstrated world-class qubit performance. Scaling to 100-1,000 qubits is the open question.

Strategic Importance to Australia

SQC represents quantum sovereignty for Australia:

• Domestic quantum hardware capability
• Not dependent on US (IBM, Google) or China quantum technology
• Academic → commercial pathway for Australian quantum research
• National security implications (defense quantum computing)

Government view: SQC is strategic national asset, like how semiconductors are strategic for Taiwan. Australia wants quantum independence.

Investment rationale: Even if SQC doesn’t become global leader, having domestic quantum capability has strategic value (defense, intelligence, research).

Comparison: SQC vs. Diraq

Both Australian, both silicon, both UNSW-connected, but different strategies:

Not competing directly: Different technical approaches to same goal (scalable silicon quantum computing). Both could succeed in different niches.