Researchers from the National Taiwan University have proposed a novel method to use the inherent gate errors of Noisy Intermediate-Scale Quantum (NISQ) devices to simulate open quantum system dynamics. This approach turns typically unwanted quantum noises into useful resources. The team demonstrated that gate errors on IBMQ cloud quantum computers can be controlled and used to simulate excitation energy transfer dynamics in a molecular exciton dimer system. This work opens new directions for the simulation of open quantum system dynamics and various stochastic systems such as in biology, finance, or cryptography.
Quantum Simulation on Noisy Quantum Computers
A team of researchers from the Department of Chemistry, Center for Quantum Science and Engineering, and Physics Division at National Taiwan University have proposed a novel scheme to utilize intrinsic gate errors of Noisy Intermediate-Scale Quantum (NISQ) devices to enable controllable simulation of open quantum system dynamics. This approach turns unwanted quantum noises into useful quantum resources.
Quantum Simulation and its Challenges
Quantum simulation represents a promising application to demonstrate quantum advantage on near-term NISQ computers. However, available quantum simulation algorithms are prone to errors and thus difficult to be realized. Contemporary quantum computers are prototypical NISQ devices, as they are subjected to various coherent and decoherent noises as well as limited in size and connectivity.
Open Quantum Systems and their Importance
The simulation of open quantum systems is a problem with significant applications. Dissipative dynamics of open quantum systems play crucial roles in a broad range of physical and chemical phenomena of complex systems such as photosynthetic light harvesting and electron transfer in organic materials. Enabling efficient and accurate simulation of open quantum system dynamics could lead to significant advances in both quantum science and technology.
Conventional Methods and their Limitations
Conventional methods for the simulation of open quantum system dynamics on classical computers are based on certain weak coupling assumptions about the underlying system-bath interactions. When these assumptions do not hold, non-perturbative treatments become necessary to yield accurate results. However, these exact methods on classical computers exhibit extremely steep scaling against the accuracy and system size, which hinders our understanding of the dynamical behaviors of complex open quantum systems.
New Approach to Quantum Simulation
The researchers propose to simulate open quantum system dynamics on quantum computers by directly exploiting the errors generated on the gate level in superconducting NISQ devices. This idea strongly differs from existing proposals. The researchers recognize that the decoherence effects induced by quantum noises are necessary and can be used as resources for simulations of open quantum systems. This approach does not require explicit engineering of the control field and no extra qubits for modeling the environment are needed either.
Quantum Simulation of Coherent Energy Transfer
The team demonstrated that gate errors on IBMQ cloud quantum computers can be controlled and utilized to simulate excitation energy transfer (EET) dynamics in a molecular exciton dimer system under tunable dissipative environments. They compared the simulation results with Hierarchical Equation of Motion (HEOM) calculations to validate that they correspond to dynamics induced by realistic system-bath interactions.
Conclusion
This work provides a new direction for quantum advantage in the NISQ era. It shows the possibility of utilizing NISQ devices as quantum noise generators as well as embracing the noises to simulate physical systems. This opens new directions for the simulation of open quantum system dynamics and various stochastic systems such as in biology, finance, or cryptography.
An article titled “Efficient Quantum Simulation of Open Quantum System Dynamics on Noisy Quantum Computers” was published on January 8, 2024, in the journal Physica Scripta. The authors of the study are Sun Shin, Li-Chai Shih, and Yuan‐Chung Cheng. The research focuses on the dynamics of open quantum systems and their simulation on noisy quantum computers. The full article can be accessed through its DOI: 10.1088/1402-4896/ad1c27.
