qumvqd-quantum-chemistry

name

qumvqd-quantum-chemistry

description

Qumode-based Variational Quantum Deflation (QumVQD) framework for excited-state quantum chemistry on bosonic quantum processors. Computes electronic and vibrational excited state energies with 1-2 orders lower gate counts than qubit-based methods. Keywords: quantum chemistry, excited states, qumode, bosonic quantum processor, variational quantum deflation, VQD, vibrational structure, electronic structure.

QumVQD: Qumode-Based Variational Quantum Deflation

Framework for computing excited-state energies of molecules on bosonic quantum processors using variational quantum deflation.

Core Concepts

Bosonic Quantum Processors

• Hardware: Harmonic oscillator-based quantum computing
• Advantage: Natural alignment with molecular vibrational structure
• Efficiency: Lower gate counts for chemistry problems

QumVQD Framework

• Method: Variational quantum deflation adapted for qumodes
• Applications: Both electronic and vibrational excited states
• Performance: 1-2 orders magnitude lower entangling gates

Technical Specifications

Electronic Structure

• Molecule Demonstrated: H2
• Accuracy: Chemical accuracy vs FCI
• Basis: STO-3G
• Constraint: Particle number conservation via Hamming weight filtering
• Hilbert Space: O(M choose n_e) vs O(2^M) for M orbitals, n_e electrons

Vibrational Structure

• Molecules: CO2, H2S
• Method: QumVQD + Hamiltonian fragmentation
• Accuracy: Spectroscopic accuracy
• Gate Count: 1-2 orders lower than qubit-based

Error Resilience

• Noise Model: Amplitude damping
• Advantage: Reduced circuit depth improves error resilience

Workflow

Electronic Structure Calculation

Step 1: Encoding

• Choose encoding: Jordan-Wigner or alternative
• Apply symmetry reduction
• Enforce particle number conservation

Step 2: Hamiltonian Preparation

• Map molecular Hamiltonian to qumode operators
• Apply Fock basis Hamming weight filtering

Step 3: Variational Optimization

• Prepare variational ansatz
• Optimize for ground state
• Apply deflation for excited states

Step 4: Energy Extraction

• Measure energy expectation values
• Validate against FCI

Vibrational Structure Calculation

Step 1: Hamiltonian Fragmentation

• Decompose via Bogoliubov transforms
• Identify normal modes

Step 2: QumVQD Execution

• Apply QumVQD to each fragment
• Combine results

Step 3: Spectroscopic Analysis

• Extract vibrational frequencies
• Compare with experimental spectra

Applications

Molecular Spectroscopy

• Vibrational energy levels
• Electronic excitations
• Photoemission spectra

Quantum Chemistry

• Reaction pathways
• Excited state dynamics
• Catalyst design

Materials Science

• Solid-state systems
• Defect properties
• Optical materials

References

• Paper: arXiv:2604.13457 - "Excited-State Quantum Chemistry on Qumode-Based Processors via Variational Quantum Deflation"
• Category: Quantum Chemistry / Bosonic Quantum Computing

Related Skills

• variational-quantum-eigensolver
• quantum-chemistry-simulation
• bosonic-quantum-computing