Nonunitary Coupled Cluster Enabled by Midcircuit Measurements on Quantum Computers

The field of chemistry is on the cusp of a revolution, thanks to the advent of quantum computers that can simulate complex chemical reactions and design new materials with unprecedented accuracy. A breakthrough in state preparation methods has reduced classical computation overhead by 28% and the number of CNOT and T gates by 57%, on average, compared to traditional protocols.

This innovation has significant implications for developing new materials and drugs, which require tremendous research effort to design, explore, and examine potential molecular candidates. By harnessing the power of quantum computers, researchers can now simulate complex chemical reactions with unprecedented accuracy, paving the way for groundbreaking discoveries in chemistry and beyond.

Quantum computers have the potential to revolutionize chemistry by simulating complex molecular systems, leading to breakthroughs in materials science and drug discovery. The advent of new specialized functional materials and drugs requires tremendous research effort to design, explore, and examine potential molecular candidates. However, the number of possible compounds is intractable for a brute-force search.

Simulating chemistry in silico may bring considerable speedup in the development process by screening out molecules with undesirable properties without having to synthesize them in laboratory. To model the quantum mechanical behavior of molecules, one must work with the Schrödinger’s equation, a linear partial differential equation. The tim-independent version of it, represented by ˆHψ = Eψ, is sufficient to observe correlation between steady-state molecular properties and simulated quantities.

The Hamiltonian (ˆH) incorporates the Born-Oppenheimer approximation, which treats nuclear and electronic degrees of freedom separately, such that the eigenvalue (E) refers to the total electronic energy. This approach has been well-studied in quantum chemistry, where generating approximate wave functions for molecular systems is a crucial step.

Quantum algorithms rely on a quality initial state for optimal performance. Preparing an initial state for specific applications can considerably reduce the cost of probabilistic algorithms such as the well-studied quantum phase estimation (QPE). In the application space of quantum chemistry, generating approximate wave functions for molecular systems is well-studied and quantum computing algorithms stand to benefit from importing these classical methods directly into a quantum circuit.

The most well-studied state preparation method for quantum chemistry on quantum computers is the variational quantum eigensolver (VQE) with a unitary coupled cluster (UCC) ansatz, whose operations are limited to unitary gates. However, this approach has limitations, and researchers have been exploring alternative methods to improve the accuracy and efficiency of quantum algorithms in chemistry.

Coupled cluster theory (CC) is a pillar of quantum chemistry on classical computers. It provides an efficient way to generate approximate wave functions for molecular systems by incorporating mid-circuit measurements into the circuit construction. This approach has been proposed as a state preparation method based on CC theory, which can be applied to quantum computers.

The coupled cluster ansatz is a powerful tool in quantum chemistry that allows researchers to describe complex electronic structures and interactions. By incorporating mid-circuit measurements, this approach can improve the accuracy of quantum algorithms in chemistry while reducing the classical computation overhead and the number of CNOT and T gates required.

Midcircuit measurements are a crucial component of the proposed state preparation method based on coupled cluster theory. By incorporating these measurements into the circuit construction, researchers can improve the accuracy of quantum algorithms in chemistry while reducing the classical computation overhead and the number of CNOT and T gates required.

The accuracy of this approach has been verified using energy evaluation and state overlap computation for a set of small chemical systems. The results show that midcircuit measurements lead to a reduction of the classical computation overhead and the number of CNOT and T gates by 28 and 57 on average when compared against the standard VQE-UCCSD protocol.

The proposed state preparation method based on coupled-cluster theory has significant implications for quantum chemistry. By improving the accuracy and efficiency of quantum algorithms in chemistry, researchers can simulate complex molecular systems more accurately and efficiently.

This approach can lead to breakthroughs in materials science and drug discovery by enabling researchers to screen out molecules with undesirable properties without having to synthesize them in laboratory. The potential applications of this research are vast, and it has the potential to revolutionize the field of chemistry.

The researchers behind this breakthrough are a team of scientists from various institutions who have been working together to develop new quantum algorithms for chemistry. Their work is focused on improving the accuracy and efficiency of quantum computers in simulating complex molecular systems.

Their research has significant implications for materials science and drug discovery, and it has the potential to revolutionize the field of chemistry. The team’s work is ongoing, and they continue to explore new ways to improve the performance of quantum algorithms in chemistry.

The next steps for this research involve further development and testing of the proposed state preparation method based on coupled cluster theory. Researchers will need to refine their approach and test it on larger chemical systems to demonstrate its scalability and accuracy.

Additionally, researchers will need to explore new ways to improve the performance of quantum algorithms in chemistry by incorporating midcircuit measurements and other advanced techniques. The potential applications of this research are vast, and it has the potential to revolutionize the field of chemistry.