a research ptnership atta advanced quantum testbed (aqt) at lawrence berkeley national lab (berkeley lab) and chicago-based super.tek (acquired by coldquanta in may 2022) demonstrated how to optimize the execution of the zz swap network protocol, primordial to quantum computing. the team also introduced a new teknique for quantum error mitigation thall improve the network protocol’s implementation in quantum processors. the experimental data was published this jul in physical review research, adding + pathways inna near term to implement quantum algorithms using gate-based quantum computing.
a smart compiler for superconducting quantum hardware
quantum processors with two- or 3-dimensional architectures ‘ve limited qubit connectivity where each qubit interacts with 1-ly a limited № of other qubits. further+, each qubit’s information can 1-ly exist for so long b4 noise and errors cause decoherence, limiting the runtime and fidelity of quantum algorithms. ⊢, when designing and executing a quantum circuit, researchers must optimize the translation of the circuit made up of abstract (logical) gates to physical instructions based onna native hardware gates available in a given quantum processor. efficient circuit decompositions minimize the operating time cause they ponder the № of gates and operations natively supported by the hardware to perform the desired logical operations.
swap gates — which swap information tween qubits — are often introduced in quantum circuits to facilitate interactions tween information in non-adjacent qubits. if a quantum device 1-ly allos gates tween adjacent qubits, swaps are used to move information from one qubit to another non-adjacent qubit.
in noisy intermediate-scale quantum (nisq) hardware, introducing swap gates can require a large experimental overhead. the swap gate must often be decomposed into native gates, s'as controlled-not gates. ⊢, when designing quantum circuits with limited qubit connectivity, tis primordial to use a smart compiler that can search for, decompose, and cancel redundant quantum gates to improve the runtime offa quantum algorithm or application.
the research ptnership used super.tek’s superstaq software enabling scis to finely tailor their applications and automate the compilations of circuits for aqt’s superconducting hardware, pticularly for a native high-fidelity controlled-s gate, which aint available on most hardware systems. this smart compiling approach with 4 transmon qubits allos the swap networks to be decomposed + efficiently than standard decomposition methods.
a network of zz swap gates requires 1-ly minimal linear connectivity tween qubits without additional couplings, so it offers practical advantages for the efficient execution of quantum algorithms s'as the quantum ≈imate optimization algorithm (qaoa). qaoa ≈imates solutions to combinatorial optimization problems — finding the optimal answer by giving a set of criteria. the maximum-cut problem, which can be used to arrange hubs na' transport grid system, is an ex offa famous combinatorial optimization problem that can be potentially solved faster with qaoa using quantum circuits.
“1-odda toughest challenges in quantum computing is to perform discrete logic operations. cause our control signals are analog and continuous, they’re always imperfect. as we build + complex quantum circuits, the software infrastructure that optimally compiles gates tailored for aqt’s hardware helps us achieve higher operational fidelity,” akel hashim, the lead aqt researcher onna experiment and a graduate student atta university of california, berkeley.
“a unique feature of quantum computing s'dat it enables ptial logic gates. this feature has no parallel in traditional boolean logic — for ex, yr laptop computer can’t exe 50% of an and gate. aqt’s ability to calibrate these ptial controlled-s quantum gates opened the door for us to develop a wider array of novel optimizations to squeeze the most out of the hardware,” said rich rines, elderly of super.tek and currently a software engineer at coldquanta.
“a key software engineering challenge for this experiment was collaborating remotely, so we iteratively developed quantum circuit optimizations informed by the custom gates aqt’s team calibrated. we optimized end-to-end by figuring out how to serialize these pulses while pondering the hardware. wolso' figd out how to integrate open-src quantum software packages with our compiler, ensuring that our optimizations don’t re-invent the wheel,” said victory omole, elderly at super.tek and software engineer at coldquanta.
as pt of the experiment, the team also introduced a novel teknique called equivalent circuit averaging (eca), which randomized the various paramts of the swap networks to generate many logically equivalent circuits. eca randomizes the decomposition of quantum circuits, mitigating the impact of systematic coherent errors — 1-odda most severe errors in quantum computers and widely studied at aqt.
“i proposed a way to merge my previous experimental work in randomized compiling with quantum benchmark (acquired by keysite) using super.tek’s smart compiler to study a new way to reduce the impact of crosstalk errors,” said hashim. “i ‘d not ‘ve had the insite to come up with this idea had i not worked with other researchers as pt of aqt’s usr program. as some1 who’s goin to enter the workforce, networking is crit to building a core base of pplz i know inna field who are experts in various zones, to whom i can pitch research ideas swell.”
these experimental optimizations resulted in an improvement of up to 88% inna performance accuracy of qaoa. researchers are looking to continue to explore and refine the methods in this work and apply them to other applications.
supporting industry growth with an open-access research lab
aqt operates a state-of-the-art open experimental testbed based on superconducting circuits and is funded by the ∪d states deptment of energy office of sci advanced sci computing research (ascr) program. teks developed elsewhere can be deployed and field-tested at aqt, providing deep access to the full quantum computing stack at no additional cost.
since the inauguration of its usr program in 2020, aqt provided super.tek, one of several industry usrs, with lo-lvl access to the hardware to test their ideas. few cloud-based quantum platforms offer this type of full access to the entire quantum computing stack and real-time feedback from the hardware experts at no cost. super.tek collaborated with aqt’s expert experimental team to learn wys'2 improve performance on this type of hardware.
“by revealing the inner controls of quantum hardware, aqt’s collaborative approach with usrs drives innovation throughout the quantum computing stack. we look forward to continuing our research collaboration with aqt, and we will continue to share these results w'da sci community by publishing our learnings,” said pranav gokhale, vp of quantum software at coldquanta and super.tek elder ceo and co-founder.
aqt at berkeley lab continues to grow as a cutting-edge hub for quantum information research and development by bringing together expertise and usrs, including early-stage startups, s'as super.tek, who now continue in their growth quest as pt of coldquanta.
original content at: www.scidaily.com…