02128nas a2200229 4500008004100000245006400041210006200105260001400167520146400181100001601645700002301661700001801684700002101702700001601723700002201739700002001761700001501781700002301796700001801819700002401837856003701861 2020 eng d00aFault-Tolerant Operation of a Quantum Error-Correction Code0 aFaultTolerant Operation of a Quantum ErrorCorrection Code c9/24/20203 a
Quantum error correction protects fragile quantum information by encoding it in a larger quantum system whose extra degrees of freedom enable the detection and correction of errors. An encoded logical qubit thus carries increased complexity compared to a bare physical qubit. Fault-tolerant protocols contain the spread of errors and are essential for realizing error suppression with an error-corrected logical qubit. Here we experimentally demonstrate fault-tolerant preparation, rotation, error syndrome extraction, and measurement on a logical qubit encoded in the 9-qubit Bacon-Shor code. For the logical qubit, we measure an average fault-tolerant preparation and measurement error of 0.6% and a transversal Clifford gate with an error of 0.3% after error correction. The result is an encoded logical qubit whose logical fidelity exceeds the fidelity of the entangling operations used to create it. We compare these operations with non-fault-tolerant protocols capable of generating arbitrary logical states, and observe the expected increase in error. We directly measure the four Bacon-Shor stabilizer generators and are able to detect single qubit Pauli errors. These results show that fault-tolerant quantum systems are currently capable of logical primitives with error rates lower than their constituent parts. With the future addition of intermediate measurements, the full power of scalable quantum error-correction can be achieved.
1 aEgan, Laird1 aDebroy, Dripto, M.1 aNoel, Crystal1 aRisinger, Andrew1 aZhu, Daiwei1 aBiswas, Debopriyo1 aNewman, Michael1 aLi, Muyuan1 aBrown, Kenneth, R.1 aCetina, Marko1 aMonroe, Christopher uhttps://arxiv.org/abs/2009.1148202376nas a2200409 4500008004100000245009100041210006900132260001500201520116700216100001801383700001701401700002201418700002001440700001901460700001901479700002301498700001901521700002101540700001901561700002201580700002001602700002201622700002201644700002101666700002201687700002301709700001901732700002001751700002701771700002201798700001801820700001901838700003001857700002401887700001801911856003701929 2019 eng d00aGround-state energy estimation of the water molecule on a trapped ion quantum computer0 aGroundstate energy estimation of the water molecule on a trapped c03/07/20193 aQuantum 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/1902.1017101947nas a2200397 4500008004100000245005400041210005400095260001500149520085000164100001801014700001601032700002301048700002301071700002201094700002401116700001901140700001801159700001801177700002001195700002501215700001801240700001801258700001901276700001901295700001601314700002301330700001901353700001701372700002401389700001901413700002201432700001901454700001901473700002001492856003701512 2019 eng d00aQuantum Computer Systems for Scientific Discovery0 aQuantum Computer Systems for Scientific Discovery c12/16/20193 aThe great promise of quantum computers comes with the dual challenges of building them and finding their useful applications. We argue that these two challenges should be considered together, by co-designing full stack quantum computer systems along with their applications in order to hasten their development and potential for scientific discovery. In this context, we identify scientific and community needs, opportunities, and significant challenges for the development of quantum computers for science over the next 2-10 years. This document is written by a community of university, national laboratory, and industrial researchers in the field of Quantum Information Science and Technology, and is based on a summary from a U.S. National Science Foundation workshop on Quantum Computing held on October 21-22, 2019 in Alexandria, VA.
1 aAlexeev, Yuri1 aBacon, Dave1 aBrown, Kenneth, R.1 aCalderbank, Robert1 aCarr, Lincoln, D.1 aChong, Frederic, T.1 aDeMarco, Brian1 aEnglund, Dirk1 aFarhi, Edward1 aFefferman, Bill1 aGorshkov, Alexey, V.1 aHouck, Andrew1 aKim, Jungsang1 aKimmel, Shelby1 aLange, Michael1 aLloyd, Seth1 aLukin, Mikhail, D.1 aMaslov, Dmitri1 aMaunz, Peter1 aMonroe, Christopher1 aPreskill, John1 aRoetteler, Martin1 aSavage, Martin1 aThompson, Jeff1 aVazirani, Umesh uhttps://arxiv.org/abs/1912.0757702892nas a2200397 4500008004100000245005600041210005500097260001500152520177700167100001701944700002301961700002101984700002202005700001902027700001602046700001902062700002502081700002302106700002002129700002002149700002602169700002302195700002402218700002202242700002302264700001602287700001302303700002002316700002402336700001702360700001902377700001802396700002302414700002002437856003702457 2019 eng d00aQuantum Simulators: Architectures and Opportunities0 aQuantum Simulators Architectures and Opportunities c12/14/20193 aQuantum simulators are a promising technology on the spectrum of quantum devices from specialized quantum experiments to universal quantum computers. These quantum devices utilize entanglement and many-particle behaviors to explore and solve hard scientific, engineering, and computational problems. Rapid development over the last two decades has produced more than 300 quantum simulators in operation worldwide using a wide variety of experimental platforms. Recent advances in several physical architectures promise a golden age of quantum simulators ranging from highly optimized special purpose simulators to flexible programmable devices. These developments have enabled a convergence of ideas drawn from fundamental physics, computer science, and device engineering. They have strong potential to address problems of societal importance, ranging from understanding vital chemical processes, to enabling the design of new materials with enhanced performance, to solving complex computational problems. It is the position of the community, as represented by participants of the NSF workshop on "Programmable Quantum Simulators," that investment in a national quantum simulator program is a high priority in order to accelerate the progress in this field and to result in the first practical applications of quantum machines. Such a program should address two areas of emphasis: (1) support for creating quantum simulator prototypes usable by the broader scientific community, complementary to the present universal quantum computer effort in industry; and (2) support for fundamental research carried out by a blend of multi-investigator, multi-disciplinary collaborations with resources for quantum simulator software, hardware, and education.
1 aAltman, Ehud1 aBrown, Kenneth, R.1 aCarleo, Giuseppe1 aCarr, Lincoln, D.1 aDemler, Eugene1 aChin, Cheng1 aDeMarco, Brian1 aEconomou, Sophia, E.1 aEriksson, Mark, A.1 aFu, Kai-Mei, C.1 aGreiner, Markus1 aHazzard, Kaden, R. A.1 aHulet, Randall, G.1 aKollár, Alicia, J.1 aLev, Benjamin, L.1 aLukin, Mikhail, D.1 aMa, Ruichao1 aMi, Xiao1 aMisra, Shashank1 aMonroe, Christopher1 aMurch, Kater1 aNazario, Zaira1 aNi, Kang-Kuen1 aPotter, Andrew, C.1 aRoushan, Pedram uhttps://arxiv.org/abs/1912.0693801499nas a2200193 4500008004100000245007800041210006900119260001500188520089900203100002401102700001401126700002101140700001601161700002301177700002301200700001701223700002801240856003701268 2019 eng d00aTwo-qubit entangling gates within arbitrarily long chains of trapped ions0 aTwoqubit entangling gates within arbitrarily long chains of trap c05/28/20193 aIon trap systems are a leading platform for large scale quantum computers. Trapped ion qubit crystals are fully-connected and reconfigurable, owing to their long range Coulomb interaction that can be modulated with external optical forces. However, the spectral crowding of collective motional modes could pose a challenge to the control of such interactions for large numbers of qubits. Here, we show that high-fidelity quantum gate operations are still possible with very large trapped ion crystals, simplifying the scaling of ion trap quantum computers. To this end, we present analytical work that determines how parallel entangling gates produce a crosstalk error that falls off as the inverse cube of the distance between the pairs. We also show experimental work demonstrating entangling gates on a fully-connected chain of seventeen 171Yb+ ions with fidelities as high as 97(1)%.
1 aLandsman, Kevin, A.1 aWu, Yukai1 aLeung, Pak, Hong1 aZhu, Daiwei1 aLinke, Norbert, M.1 aBrown, Kenneth, R.1 aDuan, Luming1 aMonroe, Christopher, R. uhttps://arxiv.org/abs/1905.1042101532nas a2200193 4500008004100000245009300041210006900134260001500203300001100218490000800229520089100237100002101128700002401149700002201173700002301195700002401218700002301242856007301265 2018 eng d00aRobust two-qubit gates in a linear ion crystal using a frequency-modulated driving force0 aRobust twoqubit gates in a linear ion crystal using a frequencym c2018/01/09 a0205010 v1203 aIn an ion trap quantum computer, collective motional modes are used to entangle two or more qubits in order to execute multi-qubit logical gates. Any residual entanglement between the internal and motional states of the ions will result in decoherence errors, especially when there are many spectator ions in the crystal. We propose using a frequency-modulated (FM) driving force to minimize such errors and implement it experimentally. In simulation, we obtained an optimized FM gate that can suppress decoherence to less than 10−4 and is robust against a frequency drift of more than ±1 kHz. The two-qubit gate was tested in a five-qubit trapped ion crystal, with 98.3(4)% fidelity for a Mølmer-Sørensen entangling gate and 98.6(7)% for a controlled-not (CNOT) gate. We also show an optimized FM two-qubit gate for 17 ions, proving the scalability of our method.
1 aLeung, Pak, Hong1 aLandsman, Kevin, A.1 aFiggatt, Caroline1 aLinke, Norbert, M.1 aMonroe, Christopher1 aBrown, Kenneth, R. uhttps://journals.aps.org/prl/abstract/10.1103/PhysRevLett.120.02050101522nas a2200133 4500008004100000245007000041210006900111260001500180520109400195100002301289700001601312700002401328856003601352 2016 eng d00aCo-Designing a Scalable Quantum Computer with Trapped Atomic Ions0 aCoDesigning a Scalable Quantum Computer with Trapped Atomic Ions c2016/02/093 aThe first generation of quantum computers are on the horizon, fabricated from quantum hardware platforms that may soon be able to tackle certain tasks that cannot be performed or modelled with conventional computers. These quantum devices will not likely be universal or fully programmable, but special-purpose processors whose hardware will be tightly co-designed with particular target applications. Trapped atomic ions are a leading platform for first generation quantum computers, but are also fundamentally scalable to more powerful general purpose devices in future generations. This is because trapped ion qubits are atomic clock standards that can be made identical to a part in 10^15, and their quantum circuit connectivity can be reconfigured through the use of external fields, without modifying the arrangement or architecture of the qubits themselves. In this article we show how a modular quantum computer of any size can be engineered from ion crystals, and how the wiring between ion trap qubits can be tailored to a variety of applications and quantum computing protocols.1 aBrown, Kenneth, R.1 aKim, Jaewan1 aMonroe, Christopher uhttp://arxiv.org/abs/1602.02840