[ { "id": "authors:6bynt-yf806", "collection": "authors", "collection_id": "6bynt-yf806", "cite_using_url": "https://authors.library.caltech.edu/records/6bynt-yf806", "type": "article", "title": "Fault-Tolerant Compiling of Classically Hard Instantaneous Quantum Polynomial Circuits on Hypercubes", "author": [ { "family_name": "Hangleiter", "given_name": "Dominik", "orcid": "0000-0002-4766-7967" }, { "family_name": "Kalinowski", "given_name": "Marcin", "orcid": "0000-0003-0605-8791" }, { "family_name": "Bluvstein", "given_name": "Dolev", "orcid": "0000-0002-9934-9530", "clpid": "Bluvstein-Dolev" }, { "family_name": "Cain", "given_name": "Madelyn", "orcid": "0000-0002-5298-3112" }, { "family_name": "Maskara", "given_name": "Nishad", "orcid": "0000-0001-5775-9542" }, { "family_name": "Gao", "given_name": "Xun" }, { "family_name": "Kubica", "given_name": "Aleksander", "orcid": "0000-0001-8213-8190", "clpid": "Kubica-Aleksander" }, { "family_name": "Lukin", "given_name": "Mikhail D." }, { "family_name": "Gullans", "given_name": "Michael J.", "orcid": "0000-0003-3974-2987" } ], "abstract": "

Realizing computationally complex quantum circuits in the presence of noise and imperfections is a challenging task. While fault-tolerant quantum computing provides a route to reducing noise, it requires a large overhead for generic algorithms. Here, we develop and analyze a hardware-efficient, fault-tolerant approach to realizing complex sampling circuits. We co-design the circuits with the appropriate quantum error-correcting codes for efficient implementation in a reconfigurable neutral atom-array architecture, constituting what we call a of the sampling algorithm. Specifically, we consider a family of \u27e62D,D,2\u27e7 quantum error-detecting codes whose transversal and permutation gate set can realize arbitrary degree-D instantaneous quantum polynomial (IQP) circuits. Using native operations of the code and the atom-array hardware, we compile a fault-tolerant and fast-scrambling family of such IQP circuits in a hypercube geometry, realized recently in the experiments by Bluvstein [Nature 626, 7997 (2024)]. We develop a theory of second-moment properties of degree-D IQP circuits for analyzing hardness and verification of random sampling by mapping to a statistical mechanics model. We provide strong evidence that sampling from these hypercube IQP circuits is classically hard to simulate even at relatively low depths. We analyze the linear cross-entropy benchmark (XEB) in comparison to the average fidelity and, depending on the local noise rate, find two different asymptotic regimes. To realize a fully scalable approach, we first show that Bell sampling from degree-4 IQP circuits is classically intractable and can be efficiently validated. We further devise new families of \u27e6O(dD),D,d\u27e7 color codes of increasing distance d, permitting exponential error suppression for transversal IQP sampling. Our results highlight fault-tolerant compiling as a powerful tool in co-designing algorithms with specific error-correcting codes and realistic hardware.

", "doi": "10.1103/prxquantum.6.020338", "issn": "2691-3399", "publisher": "American Physical Society", "publication": "PRX Quantum", "publication_date": "2025-05-28", "series_number": "2", "volume": "6", "issue": "2", "pages": "020338" }, { "id": "authors:f227n-f4x66", "collection": "authors", "collection_id": "f227n-f4x66", "cite_using_url": "https://authors.library.caltech.edu/records/f227n-f4x66", "type": "article", "title": "Fast and Parallelizable Logical Computation with Homological Product Codes", "author": [ { "family_name": "Xu", "given_name": "Qian", "orcid": "0000-0002-8738-9420", "clpid": "Xu-Qian" }, { "family_name": "Zhou", "given_name": "Hengyun", "orcid": "0000-0002-2148-8856" }, { "family_name": "Zheng", "given_name": "Guo", "orcid": "0000-0001-6338-0192" }, { "family_name": "Bluvstein", "given_name": "Dolev", "orcid": "0000-0002-9934-9530", "clpid": "Bluvstein-Dolev" }, { "family_name": "Ataides", "given_name": "J. Pablo Bonilla", "orcid": "0000-0001-5518-7907" }, { "family_name": "Lukin", "given_name": "Mikhail D.", "orcid": "0000-0002-8658-1007" }, { "family_name": "Jiang", "given_name": "Liang", "orcid": "0000-0002-0000-9342" } ], "abstract": "

Quantum error correction is necessary to perform large-scale quantum computation but requires extremely large overheads in both space and time. High-rate quantum low-density-parity-check (qLDPC) codes promise a route to reduce qubit numbers, but performing computation while maintaining low space cost has required serialization of operations and extra time costs. In this work, we design fast and parallelizable logical gates for qLDPC codes and demonstrate their utility for key algorithmic subroutines such as the quantum adder. Our gate gadgets utilize transversal logical cnots between a data qLDPC code and a suitably constructed ancilla code to perform parallel Pauli product measurements (PPMs) on the data logical qubits. For hypergraph product codes, we show that the ancilla can be constructed by simply modifying the base classical codes of the data code, achieving parallel PPMs on a subgrid of the logical qubits with a lower space-time cost than existing schemes for an important class of circuits. Generalizations to 3D and 4D homological product codes further feature fast PPMs in constant depth. While prior work on qLDPC codes has focused on individual logical gates, we initiate the study of fault-tolerant compilation with our expanded set of native qLDPC code operations, constructing algorithmic primitives for preparing \ud835\udc58-qubit Greenberger-Horne-Zeilinger states and distilling or teleporting \ud835\udc58 magic states with \ud835\udc42\u2061(1) space overhead in \ud835\udc42\u2061(1) and \ud835\udc42\u2061(√\ud835\udc58\u2062log\u2061\ud835\udc58) logical cycles, respectively. We further generalize this to key algorithmic subroutines, demonstrating the efficient implementation of quantum adders using parallel operations. Our constructions are naturally compatible with reconfigurable architectures such as neutral atom arrays, paving the way to large-scale quantum computation with low space and time overheads.

", "doi": "10.1103/physrevx.15.021065", "issn": "2160-3308", "publisher": "American Physical Society", "publication": "Physical Review X", "publication_date": "2025-05-22", "series_number": "2", "volume": "15", "issue": "2", "pages": "021065" }, { "id": "authors:622kn-n6p59", "collection": "authors", "collection_id": "622kn-n6p59", "cite_using_url": "https://authors.library.caltech.edu/records/622kn-n6p59", "type": "article", "title": "Constant-overhead fault-tolerant quantum computation with reconfigurable atom arrays", "author": [ { "family_name": "Xu", "given_name": "Qian", "orcid": "0000-0002-8738-9420", "clpid": "Xu-Qian" }, { "family_name": "Bonilla Ataides", "given_name": "J. Pablo", "orcid": "0000-0001-5518-7907", "clpid": "Bonilla-Ataides-Juan-Pablo" }, { "family_name": "Pattison", "given_name": "Christopher A." }, { "family_name": "Raveendran", "given_name": "Nithin", "orcid": "0000-0002-1024-8099", "clpid": "Raveendran-Nithin" }, { "family_name": "Bluvstein", "given_name": "Dolev", "orcid": "0000-0002-9934-9530", "clpid": "Bluvstein-Dolev" }, { "family_name": "Wurtz", "given_name": "Jonathan", "orcid": "0000-0001-7237-0789", "clpid": "Wurtz-Jonathan" }, { "family_name": "Vasi\u0107", "given_name": "Bane", "orcid": "0000-0003-2365-4106", "clpid": "Vasi\u0107-Bane" }, { "family_name": "Lukin", "given_name": "Mikhail D.", "orcid": "0000-0002-8658-1007", "clpid": "Lukin-Mikhail-D" }, { "family_name": "Jiang", "given_name": "Liang", "orcid": "0000-0002-0000-9342", "clpid": "Jiang-Liang" }, { "family_name": "Zhou", "given_name": "Hengyun", "orcid": "0000-0002-2148-8856", "clpid": "Zhou-Hengyun" } ], "abstract": "
\n
\n

Quantum low-density parity-check (qLDPC) codes can achieve high encoding rates and good code distance scaling, potentially enabling low-overhead fault-tolerant quantum computing. However, implementing qLDPC codes involves nonlocal operations that require long-range connectivity between qubits. This makes their physical realization challenging in comparison to geometrically local codes, such as the surface code. Here we propose a hardware-efficient scheme for fault-tolerant quantum computation with high-rate qLDPC codes that is compatible with the recently demonstrated capabilities of reconfigurable atom arrays. Our approach utilizes the product structure inherent in many qLDPC codes to implement the nonlocal syndrome extraction circuit through atom rearrangement, resulting in an effectively constant overhead. We prove the fault tolerance of these protocols, and our simulations show that the qLDPC-based architecture starts to outperform the surface code with as few as several hundred physical qubits. We further find that quantum algorithms involving thousands of logical qubits can be performed using less than 105 physical qubits. Our work suggests that low-overhead quantum computing with qLDPC codes is within reach using current experimental technologies.

\n
\n
", "doi": "10.1038/s41567-024-02479-z", "issn": "1745-2473", "publisher": "Nature Publishing Group", "publication": "Nature Physics", "publication_date": "2024-07", "volume": "20", "pages": "1084-1090" }, { "id": "authors:n452x-qnv12", "collection": "authors", "collection_id": "n452x-qnv12", "cite_using_url": "https://authors.library.caltech.edu/records/n452x-qnv12", "type": "article", "title": "High-fidelity parallel entangling gates on a neutral-atom quantum computer", "author": [ { "family_name": "Evered", "given_name": "Simon J.", "orcid": "0000-0001-8986-1103" }, { "family_name": "Bluvstein", "given_name": "Dolev", "orcid": "0000-0002-9934-9530", "clpid": "Bluvstein-Dolev" }, { "family_name": "Kalinowski", "given_name": "Marcin", "orcid": "0000-0003-0605-8791" }, { "family_name": "Ebadi", "given_name": "Sepehr" }, { "family_name": "Manovitz", "given_name": "Tom", "orcid": "0000-0003-3470-1369" }, { "family_name": "Zhou", "given_name": "Hengyun" }, { "family_name": "Li", "given_name": "Sophie H." }, { "family_name": "Geim", "given_name": "Alexandra A.", "orcid": "0000-0001-5294-4941" }, { "family_name": "Wang", "given_name": "Tout T.", "orcid": "0000-0003-3107-2579" }, { "family_name": "Maskara", "given_name": "Nishad" }, { "family_name": "Levine", "given_name": "Harry" }, { "family_name": "Semeghini", "given_name": "Giulia" }, { "family_name": "Greiner", "given_name": "Markus", "orcid": "0000-0002-2935-2363" }, { "family_name": "Vuleti\u0107", "given_name": "Vladan", "orcid": "0000-0002-9786-0538" }, { "family_name": "Lukin", "given_name": "Mikhail D.", "orcid": "0000-0002-8658-1007" } ], "abstract": "

The ability to perform entangling quantum operations with low error rates in a scalable fashion is a central element of useful quantum information processing1. Neutral-atom arrays have recently emerged as a promising quantum computing platform, featuring coherent control over hundreds of qubits2,3 and any-to-any gate connectivity in a flexible, dynamically reconfigurable architecture4. The main outstanding challenge has been to reduce errors in entangling operations mediated through Rydberg interactions5. Here we report the realization of two-qubit entangling gates with 99.5% fidelity on up to 60 atoms in parallel, surpassing the surface-code threshold for error correction6,7. Our method uses fast, single-pulse gates based on optimal control8, atomic dark states to reduce scattering9 and improvements to Rydberg excitation and atom cooling. We benchmark fidelity using several methods based on repeated gate applications10,11, characterize the physical error sources and outline future improvements. Finally, we generalize our method to design entangling gates involving a higher number of qubits, which we demonstrate by realizing low-error three-qubit gates12,13. By enabling high-fidelity operation in a scalable, highly connected system, these advances lay the groundwork for large-scale implementation of quantum algorithms14, error-corrected circuits7 and digital simulations15.

", "doi": "10.1038/s41586-023-06481-y", "pmcid": "PMC10567572", "issn": "0028-0836", "publisher": "Nature Publishing Group", "publication": "Nature", "publication_date": "2023-10-11", "series_number": "7982", "volume": "622", "issue": "7982", "pages": "268-272" }, { "id": "authors:2wqgt-6ev32", "collection": "authors", "collection_id": "2wqgt-6ev32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220505-221358148", "type": "article", "title": "Quantum optimization of maximum independent set using Rydberg atom arrays", "author": [ { "family_name": "Ebadi", "given_name": "S.", "orcid": "0000-0003-4146-3637", "clpid": "Ebadi-Sepehr" }, { "family_name": "Keesling", "given_name": "A.", "orcid": "0000-0003-3931-0949", "clpid": "Keesling-Alexander" }, { "family_name": "Cain", "given_name": "M.", "orcid": "0000-0002-5298-3112", "clpid": "Cain-Madelyn" }, { "family_name": "Wang", "given_name": "T. T.", "orcid": "0000-0003-3107-2579", "clpid": "Wang-Tout-T" }, { "family_name": "Levine", "given_name": "H.", "orcid": "0000-0001-8270-3233", "clpid": "Levine-Harry" }, { "family_name": "Bluvstein", "given_name": "D.", "orcid": "0000-0002-9934-9530", "clpid": "Bluvstein-Dolev" }, { "family_name": "Semeghini", "given_name": "G.", "orcid": "0000-0001-9071-2279", "clpid": "Semeghini-Giulia" }, { "family_name": "Omran", "given_name": "A.", "orcid": "0000-0002-2253-0278", "clpid": "Omran-Ahmed" }, { "family_name": "Liu", "given_name": "J.-G.", "orcid": "0000-0003-1635-2679", "clpid": "Liu-Jinguo" }, { "family_name": "Samajdar", "given_name": "R.", "orcid": "0000-0001-5171-7798", "clpid": "Samajdar-Rhine" }, { "family_name": "Luo", "given_name": "X.-Z.", "clpid": "Luo-Xiu-Zhe" }, { "family_name": "Nash", "given_name": "B.", "clpid": "Nash-Beatrice" }, { "family_name": "Gao", "given_name": "X.", "clpid": "Gao-Xun" }, { "family_name": "Barak", "given_name": "B.", "orcid": "0000-0002-4053-8927", "clpid": "Barak-Boaz" }, { "family_name": "Farhi", "given_name": "E.", "orcid": "0000-0002-7309-8489", "clpid": "Farhi-Edward" }, { "family_name": "Sachdev", "given_name": "S.", "orcid": "0000-0002-2432-7070", "clpid": "Sachdev-Subir" }, { "family_name": "Gemelke", "given_name": "N.", "orcid": "0000-0001-9911-4275", "clpid": "Gemelke-Nathan" }, { "family_name": "Zhou", "given_name": "L.", "orcid": "0000-0001-7598-8621", "clpid": "Zhou-Leo" }, { "family_name": "Choi", "given_name": "S.", "orcid": "0000-0002-1247-062X", "clpid": "Choi-Soonwon" }, { "family_name": "Pichler", "given_name": "H.", "orcid": "0000-0003-2144-536X", "clpid": "Pichler-Hannes" }, { "family_name": "Wang", "given_name": "S.-T.", "orcid": "0000-0003-1403-5901", "clpid": "Wang-Shengtao" }, { "family_name": "Greiner", "given_name": "M.", "orcid": "0000-0002-2935-2363", "clpid": "Greiner-Markus" }, { "family_name": "Vuleti\u0107", "given_name": "V.", "orcid": "0000-0002-9786-0538", "clpid": "Vuleti\u0107-Vladan" }, { "family_name": "Lukin", "given_name": "M. D.", "orcid": "0000-0002-8658-1007", "clpid": "Lukin-Mikhail-D" } ], "abstract": "Realizing quantum speedup for practically relevant, computationally hard problems is a central challenge in quantum information science. Using Rydberg atom arrays with up to 289 qubits in two spatial dimensions, we experimentally investigate quantum algorithms for solving the maximum independent set problem. We use a hardware-efficient encoding associated with Rydberg blockade, realize closed-loop optimization to test several variational algorithms, and subsequently apply them to systematically explore a class of graphs with programmable connectivity. We find that the problem hardness is controlled by the solution degeneracy and number of local minima, and we experimentally benchmark the quantum algorithm's performance against classical simulated annealing. On the hardest graphs, we observe a superlinear quantum speedup in finding exact solutions in the deep circuit regime and analyze its origins.", "doi": "10.1126/science.abo6587", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "2022-06-10", "series_number": "6598", "volume": "376", "issue": "6598", "pages": "1209-1215" }, { "id": "authors:zvxqz-j2a42", "collection": "authors", "collection_id": "zvxqz-j2a42", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220520-231737000", "type": "article", "title": "Dispersive optical systems for scalable Raman driving of hyperfine qubits", "author": [ { "family_name": "Levine", "given_name": "Harry", "orcid": "0000-0001-8270-3233", "clpid": "Levine-Harry" }, { "family_name": "Bluvstein", "given_name": "Dolev", "orcid": "0000-0002-9934-9530", "clpid": "Bluvstein-Dolev" }, { "family_name": "Keesling", "given_name": "Alexander", "orcid": "0000-0003-3931-0949", "clpid": "Keesling-Alexander" }, { "family_name": "Wang", "given_name": "Tout T.", "orcid": "0000-0003-3107-2579", "clpid": "Wang-Tout-T" }, { "family_name": "Ebadi", "given_name": "Sepehr", "orcid": "0000-0003-4146-3637", "clpid": "Ebadi-Sepehr" }, { "family_name": "Semeghini", "given_name": "Giulia", "orcid": "0000-0001-9071-2279", "clpid": "Semeghini-Giulia" }, { "family_name": "Omran", "given_name": "Ahmed", "orcid": "0000-0002-2253-0278", "clpid": "Omran-Ahmed" }, { "family_name": "Greiner", "given_name": "Markus", "orcid": "0000-0002-2935-2363", "clpid": "Greiner-Markus" }, { "family_name": "Vuleti\u0107", "given_name": "Vladan", "orcid": "0000-0002-9786-0538", "clpid": "Vuleti\u0107-Vladan" }, { "family_name": "Lukin", "given_name": "Mikhail D.", "orcid": "0000-0002-8658-1007", "clpid": "Lukin-Mikhail-D" } ], "abstract": "Hyperfine atomic states are among the most promising candidates for qubit encoding in quantum information processing. In atomic systems, hyperfine transitions are typically driven through a two-photon Raman process by a laser field which is amplitude modulated at the hyperfine qubit frequency. Here we introduce a method for generating amplitude modulation by phase modulating a laser and reflecting it from a highly dispersive optical element known as a chirped Bragg grating. This approach is passively stable, offers high efficiency, and is compatible with high-power laser sources, enabling large Rabi frequencies and improved quantum coherence. We benchmark this approach by globally driving an array of approximately 300 neutral \u2078\u2077Rb atomic qubits trapped in optical tweezers and obtain Rabi frequencies of 2 MHz with photon-scattering error rates of less than 2 \u00d7 10\u207b\u2074 per \u03c0 pulse. This robust approach can be directly integrated with local addressing optics in both neutral atom and trapped ion systems to facilitate high-fidelity single-qubit operations for quantum information processing.", "doi": "10.1103/physreva.105.032618", "issn": "2469-9926", "publisher": "American Physical Society", "publication": "Physical Review A", "publication_date": "2022-03", "series_number": "3", "volume": "105", "issue": "3", "pages": "Art. No. 032618" } ]