Quantum Computing from the Ground Up

Andreas H. Trabesinger

Giuseppe Castagnoli, David Finkelstein

Systems of spin 1, such as triplet pairs of spin-1/2 fermions (like orthohydrogen nuclei) make useful three-terminal elements for quantum computation, and when interconnected by qubit equality relations are universal for quantum computation. This is an instance of quantum-statistical computation: some of the logical relations of the problem are satisfied identically in virtue of quantum statistics, which takes no time. We show heuristically that quantum-statistical ground-mode computation is substantially faster than pure ground-mode computation when the ground mode is reached by annealing.

Mikio Nakahara

Alan Bidart, Prateek Vaish, Tilas Kabengele +3 more

Quantum computing offers the promise of revolutionizing quantum chemistry by enabling the solution of chemical problems for substantially less computational cost. While most demonstrations of quantum computation to date have focused on resolving the energies of the electronic ground states of small molecules, the field of quantum chemistry is far broader than ground-state chemistry; equally important to practicing chemists are chemical reaction dynamics and reaction mechanism prediction. Here, we review progress toward and the potential of quantum computation for understanding quantum chemistry beyond the ground state, including for reaction mechanisms, reaction dynamics, and finite-temperature quantum chemistry. We discuss algorithmic and other considerations these applications share, as well as differences that make them unique. We also highlight the potential speedups these applications may realize and challenges they may face. We hope that this discussion stimulates further research into how quantum computation may better inform experimental chemistry in the future.

Ari Mizel, Morgan W. Mitchell, Marvin L. Cohen

We study design challenges associated with realizing a ground-state quantum computer. In such a computer, it is necessary that the energy gap between the ground state and first excited state be sufficiently large to prevent disruptive excitations. Here, an estimate of this gap is provided as a function of computer size. We then address the problem of detecting the output of a ground-state quantum computer. It is shown that the exponential detection difficulties that appear to be present at first can be overcome by small design changes.