Quantum Embedding and Quantum Simulations
We develop quantum embedding theories and codes to investigate strongly correlated states of spin qubits and their coherence properties. The quantum embedding techniques are based on methods using many body perturbation theory. We investigate quantum bits in semiconductors and insulators, on both classical and quantum computers.
Quantum Defect Embedding Theory (QDET)
We developed a quantum embedding theory for the calculation of strongly-correlated electronic states of active regions, with the rest of the system described within density functional theory. We implemented the theory in the WEST code, enabling calculations for large systems, with hundreds of atoms. We are investigating spin-defects in semiconductors and insulators, including diamond, SiC and MgO and h-BN.
- "Optical Properties of Neutral F Centers in Bulk MgO with Density Matrix Embedding", Shreya Verma, Abhishek Mitra, Yu Jin, Soumi Haldar, Christian Vorwerk, Matthew R. Hermes, Giulia Galli, Laura Gagliardi, J. Phys. Chem. Lett. 14, 7703–7710 (2023).
- "Disentangling photoexcitation and photoluminescence processes in defective MgO", Christian Vorwerk and Giulia Galli, Phys. Rev. Mater. 7, 033801 (2023).
- "Green's function formulation of quantum defect embedding theory", Nan Sheng*, Christian Vorwerk*, Marco Govoni, and Giulia Galli (*equal contribution), J. Chem. Theory Comput. 18, 3512 (2022).
- "First-principles predictions of out-of-plane group IV and V dimers as high-symmetry high-spin defects in hexagonal boron nitride", Jooyong Bhang, He Ma, Donggyu Yim, Giulia Galli, and Hosung Seo, ACS Appl. Mater. Interfaces 13, 45768–45777 (2021).
- "Quantum Embedding Theory for Strongly-correlated States in Materials", He Ma, Nan Sheng, Marco Govoni and Giulia Galli, J. Chem. Theory Comput. 17, 2116 (2021).
- "Quantum simulations of materials on near-term quantum computers", He Ma, Marco Govoni and Giulia Galli, Npj Comput. Mat. 6, 85 (2020).
- "First-principles Studies of Strongly Correlated States in Defect Spin Qubits in Diamond", He Ma, Nan Sheng, Marco Govoni and Giulia Galli, Phys. Chem. Chem. Phys. 22, 25522 (2020).
Quantum Simulations on Quantum Computers
We combined a qubit-efficient encoding and a qubit coupled-cluster ansatz to simulate the electronic properties of spin defects in solids on quantum computers. We developed a strategy leading to a substantial improvement in the scaling of circuit gate counts and in the number of required qubits, and to the decrease in the number of required variational parameters, thus increasing resilience to noise. We showed that use of noise extrapolation greatly improves the accuracy of ground state energy and calculated transitions on quantum hardware.
- "Quantum simulations of Fermionic Hamiltonians with efficient encoding and ansatz schemes", Benchen Huang, Nan Sheng, Marco Govoni, and Giulia Galli, J. Chem. Theory Comput. 19, 1487–1498 (2023).
- "Quantum Embedding Theories to Simulate Condensed Systems on Quantum Computers", Christian Vorwerk*, Nan Sheng*, Marco Govoni, Benchen Huang, and Giulia Galli (*equal contribution), Nat. Comput. Sci. 2, 424 (2022).
- "Simulating the electronic structure of spin defects on quantum computers", Benchen Huang, Marco Govoni, and Giulia Galli, PRX Quantum 3, 010339 (2022).
- "Quantum Monte Carlo on Quantum Computers", Benchen Huang et al., AWS Quantum Technologies Blog (2022).
- "Quantum simulations of materials on near-term quantum computers", He Ma, Marco Govoni and Giulia Galli, Npj Comput. Mat. 6, 85 (2020).