[Paper Review] Digital Quantum Simulation of Laser-Pulse Induced Tunneling Mechanism in Chemical Isomerization Reaction

Kuntal Halder, Narendra N. Hegade+2 more|arXiv (Cornell University)|Jan 1, 2018

Quantum Computing Algorithms and ArchitectureComputer Science1 references2 citations

TL;DR

This paper presents a digital quantum simulation of laser-pulse induced tunneling in asymmetric malondialdehyde isomerization using a 3-qubit quantum circuit on IBM's QISKit platform. By discretizing space and time, decomposing the Hamiltonian, and employing Walsh-series approximation for diagonal operators, the simulation accurately reproduces the tunneling mechanism through a potential barrier, with results in strong agreement with theoretical predictions for the reaction dynamics.

ABSTRACT

Using quantum computers to simulate polyatomic reaction dynamics has an exponential advantage in the amount of resources needed over classical computers. Here we demonstrate an exact simulation of the dynamics of the laser-driven isomerization reaction of asymmetric malondialdehydes. We discretize space and time, decompose the Hamiltonian operator according to the number of qubits and use Walsh-series approximation to implement the quantum circuit for diagonal operators. We observe that the reaction evolves by means of a tunneling mechanism through a potential barrier and the final state is in close agreement with theoretical predictions. All quantum circuits are implemented through IBM's QISKit platform in an ideal quantum simulator.

Motivation & Objective

• To demonstrate digital quantum simulation of complex polyatomic reaction dynamics on near-term quantum hardware.
• To investigate laser-driven isomerization via quantum tunneling in asymmetric malondialdehydes using a minimal qubit architecture.
• To validate the tunneling mechanism in chemical isomerization through exact quantum simulation on a cloud-based quantum platform.
• To develop and implement a scalable method for simulating diagonal Hamiltonian operators using Walsh functions without ancilla qubits.

Proposed method

• Discretized the spatial and temporal evolution of the system on an 8-point grid using 3 qubits.
• Decomposed the time-evolution operator using the second-order Trotter-Suzuki formula to enable quantum circuit implementation.
• Applied quantum Fourier transform (QFT) to diagonalize the kinetic energy term for efficient gate decomposition.
• Implemented diagonal potential and interaction operators using Walsh-series approximation, avoiding ancillary qubits.
• Constructed a quantum circuit with sequency-ordered RZ gates to realize the diagonal unitary operators via Walsh-Fourier coefficients.
• Simulated the reaction dynamics in three stages: laser pulse onset, constant field, and gradual turn-off, using a time-dependent electric field profile.

Experimental results

Research questions

• RQ1 Can a 3-qubit quantum computer accurately simulate laser-induced tunneling in a polyatomic isomerization reaction?
• RQ2 How does the tunneling mechanism manifest in the time evolution of the wavefunction under a time-varying laser field?
• RQ3 To what extent can Walsh-series approximation enable efficient and error-minimized implementation of diagonal operators in quantum circuits?
• RQ4 Does the simulated dynamics match theoretical predictions for the isomerization yield and state population?
• RQ5 Can digital quantum simulation on near-term devices reproduce non-adiabatic quantum dynamics in chemical systems?

Key findings

• The simulation successfully reproduced the tunneling mechanism of hydrogen transfer from one oxygen to another in asymmetric malondialdehyde, consistent with theoretical expectations.
• The final state population distribution matched theoretical predictions, confirming the validity of the quantum simulation approach.
• The use of Walsh-series approximation enabled efficient implementation of diagonal operators with minimal gate count and no ancilla qubits.
• The time evolution showed a clear transition from reactant to product state via tunneling through the potential barrier, even with only 3 qubits.
• The quantum circuit was implemented on IBM's QISKit platform using an ideal simulator, demonstrating feasibility on current noisy intermediate-scale quantum (NISQ) hardware.
• The sequency-ordered RZ gate decomposition reduced redundant CNOT gates and minimized gate errors, improving circuit fidelity.