New technique to systematically discover optimum qua

Figure 1

picture: Quantum operation sequence (conceptual diagram)
The six horizontal blue traces characterize six qubits, with the enter on the left and the output on the appropriate. Operations are executed from left to proper. Every purple sq. represents a 1-qubit operation, and every inexperienced vertical line connecting two blue traces represents a 2-qubit operation. The optimum quantum operation sequence is realized with the fewest operations.

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Credit score: Nationwide Institute of Info and Communications Know-how (NICT); Keio College; Tokyo College of Science; Faculty of Science, The College of Tokyo


– Developed a brand new technique for locating optimum quantum operation sequences for quantum computer systems
– Based mostly on GRAPE, the brand new technique systematically finds quantum operation sequences and permits environment friendly process execution
– Anticipated to contribute to bettering the efficiency of quantum computer systems and lowering environmental affect


The Nationwide Institute of Info and Communications Know-how (NICT, President: TOKUDA Hideyuki, Ph.D.), Keio College (President: ITOH Kohei, Ph.D.), Tokyo College of Science (President: Dr. ISHIKAWA Masatoshi), The College of Tokyo (President: Dr. FUJII Teruo), succeeded for the primary time in growing a way for systematically discovering the optimum quantum operation sequence for a quantum pc.

To ensure that a quantum pc to carry out a process, we have to write a sequence of quantum operations. Till now, pc operators have written their very own quantum operation sequences primarily based on present strategies (recipes). What we now have developed this time is a scientific technique that applies optimum management concept (GRAPE algorithm) to determine the theoretically optimum sequence from amongst all conceivable quantum operation sequences.

This technique is anticipated to develop into a great tool for medium-scale quantum computer systems and is anticipated to contribute to bettering the efficiency of quantum computer systems and lowering environmental affect within the close to future.

This consequence was printed within the American scientific journal “Bodily Assessment A” on August 23, 2022.


Quantum computer systems, that are presently beneath growth, are anticipated to have a serious affect on society. Their advantages embody lowering the environmental burden by lowering vitality consumption, discovering new chemical substances for medical use, accelerating the seek for supplies for a cleaner atmosphere, and so forth.

One of many large issues for quantum computer systems is that the quantum state could be very delicate to noise, so it’s tough to take care of it stably for a very long time (sustaining a coherent quantum state). With a purpose to acquire one of the best efficiency, it’s obligatory to finish the operations inside the time that the coherent quantum state is maintained. There was a necessity for a way to systematically determine the optimum sequences.


The analysis staff has developed a scientific technique to determine the optimum quantum operation sequence.

When a pc shops and processes info, all info is transformed to a string of bits with values of 0 or 1. A quantum operation sequence is a pc program written in a human-readable language that’s transformed in order that it may be processed by a quantum pc (see Determine 1). The quantum operation sequence consists of 1-qubit operations and 2-qubit operations. One of the best sequence is the one with the fewest operations and exhibits one of the best efficiency (the variety of purple squares and inexperienced vertical traces is the smallest).

The brand new technique analyzes all potential sequences of elementary quantum operations utilizing a computational algorithm referred to as GRAPE, a numerical optimum management concept algorithm. Particularly, we create a desk of quantum operation sequences and the efficiency index (constancy F) for every sequence, starting from hundreds to hundreds of thousands, relying on the variety of qubits and the variety of operations beneath investigation. The optimum quantum operation sequence is systematically recognized primarily based on the amassed knowledge. Determine 2 exhibits the connection between the size of the quantum operation sequence and its efficiency index, and it may be seen that if the variety of qubits n is 4, 5 or extra 2-qubit gates are required.

It’s also potential for the brand new technique to research the whole checklist of all quantum operation sequences and consider typical recipes. As such, it may possibly present a helpful instrument for establishing benchmarks for previous and future analysis on the efficiency of few-qubit quantum algorithms.

[Future prospects]

The systematic technique to search out the optimum quantum operation sequence for quantum computer systems is anticipated to develop into a great tool for medium-scale quantum computer systems. Within the close to future, it’s anticipated to enhance the efficiency of quantum computer systems (see Determine 3) and contribute to lowering the burden on the atmosphere.

We additionally discovered that there are lots of optimum sequences of quantum operations which can be wonderful. Because of this a probabilistic strategy might prolong the applicability of this new technique to bigger duties. Approaches primarily based on analyzing giant datasets counsel the opportunity of integrating machine studying with our new technique to additional improve the predictive energy. Sooner or later, the analysis staff will apply the outcomes obtained this time to the optimization of duties obtained from precise quantum algorithms.

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