Superconducting Circuit QED for Quantum Annealing, Computing, and Simulation

Andrew J. Kerman

Masaaki Maezawa, Go Fujii, Mutsuo Hidaka +8 more

We propose a prime factorizer operated in a framework of quantum annealing (QA). The idea is inverse operation of a multiplier implemented with QA-based Boolean logic circuits. We designed the QA machine on an application-specific-annealing-computing architecture which efficiently increases available hardware budgets at the cost of restricted functionality. The invertible operation of QA logic gates consisting of superconducting flux qubits was confirmed by circuit simulation with classical noise sources. The circuits were implemented and fabricated by using superconducting integrated circuit technologies with Nb/AlOx/Nb Josephson junctions. We also propose a 2.5Dimensional packaging scheme of a qubit-chip/interpose /package-substrate structure for realizing practically large-scale QA systems.

Jens Koch

Daisuke Saida, Mutsuo Hidaka, Yuki Yamanashi

Prime factorization (P=M×N) is considered to be a promising application in quantum computations. We perform 4-bit factorization in experiments using a superconducting flux qubit toward quantum annealing (QA). Our proposed method uses a superconducting quantum circuit implementing a multiplier Hamiltonian, which provides combinations ofMandNas a factorization solution after QA when the integerPis initially set. The circuit comprises multiple multiplier units (MUs) combined with connection qubits. The key points are a native implementation of the multiplier Hamiltonian to the superconducting quantum circuit and its fabrication using a Nb multilayer process with a Josephson junction dedicated to the qubit. The 4-bit factorization circuit comprises 32 superconducting flux qubits. Our method has superior scalability because the Hamiltonian is implemented with fewer qubits than in conventional methods using a chimera graph architecture. We perform experiments at 10 mK to clarify the validity of interconnections of a MU using qubits. We demonstrate experiments at 4.2 K and simulations for the factorization of integers four, six, and nine.

Denis Melanson

The field of quantum information has been a fast growing field of research in the last few decades. The reason for this development is the potentially immense power of quantum computers, capable of solving hard problems in a fraction of the time it would take a classical computer. Quantum annealers are a type of quantum computer that seek to solve computational problems by finding the ground state of a quantum system. This type of quantum computer has been implemented on a large scale using superconducting flux quantum bits, but the computational power is limited. One potential improvement to help in this context is the implementation of multi-body interactions between quantum bits. Many-body interactions would be useful in allowing quantum annealers to solve more complex problems that are relevant in various areas of quantum information and science and implementing quantum error correction. \n \nWe present a superconducting device that implements a strong and tunable in sign and magnitude three-body interaction between superconducting flux quantum bits. The circuit design proposed has vanishing two-body interactions and robustness against noise and parameter variations. This circuit behaves as an ideal computational basis ZZZ coupler in a simulated three-qubit quantum annealing experiment. These properties are confirmed by calculations based on the Born-Oppenheimer approximation, a two-level spin model for the coupling circuit, and full numerical diagonalization. \n \nThe proposed circuit is based on already available technology and therefore could be readily implemented in the next generation of quantum annealing hardware. This work will be relevant for advanced quantum annealing protocols and future developments of high-order many-body interactions in quantum computers and simulators.

Leszek Jaroszynski