Quantum computing leverages the quantum resources of superposition and entanglement to efficiently solve computational problems considered intractable for classical computers. Examples include calculating molecular and nuclear structure, simulating strongly-interacting electron systems, and modeling aspects of material function. While substantial theoretical advances have been made in mapping these problems to quantum algorithms, there remains a large gap between the resource requirements for solving such problems and the capabilities of currently available quantum hardware. Bridging this gap will require a co-design approach, where the expression of algorithms is developed in conjunction with the hardware itself to optimize execution. Here, we describe a scalable co-design framework for solving chemistry problems on a trapped ion quantum computer, and apply it to compute the ground-state energy of the water molecule. The robust operation of the trapped ion quantum computer yields energy estimates with errors approaching the chemical accuracy, which is the target threshold necessary for predicting the rates of chemical reaction dynamics.

1 aNam, Yunseong1 aChen, Jwo-Sy1 aPisenti, Neal, C.1 aWright, Kenneth1 aDelaney, Conor1 aMaslov, Dmitri1 aBrown, Kenneth, R.1 aAllen, Stewart1 aAmini, Jason, M.1 aApisdorf, Joel1 aBeck, Kristin, M.1 aBlinov, Aleksey1 aChaplin, Vandiver1 aChmielewski, Mika1 aCollins, Coleman1 aDebnath, Shantanu1 aDucore, Andrew, M.1 aHudek, Kai, M.1 aKeesan, Matthew1 aKreikemeier, Sarah, M.1 aMizrahi, Jonathan1 aSolomon, Phil1 aWilliams, Mike1 aWong-Campos, Jaime, David1 aMonroe, Christopher1 aKim, Jungsang uhttps://arxiv.org/abs/1902.1017101470nas a2200205 4500008004100000245006500041210006400106260001500170300001400185490000800199520087200207100001701079700002201096700002001118700002101138700002301159700002501182700002001207856003701227 2013 eng d00aAll-Optical Switch and Transistor Gated by One Stored Photon0 aAllOptical Switch and Transistor Gated by One Stored Photon c2013/07/04 a768 - 7700 v3413 a The realization of an all-optical transistor where one 'gate' photon controls a 'source' light beam, is a long-standing goal in optics. By stopping a light pulse in an atomic ensemble contained inside an optical resonator, we realize a device in which one stored gate photon controls the resonator transmission of subsequently applied source photons. A weak gate pulse induces bimodal transmission distribution, corresponding to zero and one gate photons. One stored gate photon produces fivefold source attenuation, and can be retrieved from the atomic ensemble after switching more than one source photon. Without retrieval, one stored gate photon can switch several hundred source photons. With improved storage and retrieval efficiency, our work may enable various new applications, including photonic quantum gates, and deterministic multiphoton entanglement. 1 aChen, Wenlan1 aBeck, Kristin, M.1 aBücker, Robert1 aGullans, Michael1 aLukin, Mikhail, D.1 aTanji-Suzuki, Haruka1 aVuletic, Vladan uhttp://arxiv.org/abs/1401.3194v1