Small quantum circuits that are key to quantum computing

Till J. Weinhold, Jeremy L. O’Brien, Geoff J. Pryde +1 more

Gunajit Kalita

J.-H. Bae, Paul M. Alsing, Doyeol Ahn +1 more

Every quantum algorithm is represented by set of quantum circuits. Any optimization scheme for a quantum algorithm and quantum computation is very important especially in the arena of quantum computation with limited number of qubit resources. Major obstacle to this goal is the large number of elemental quantum gates to build even small quantum circuits. Here, we propose and demonstrate a general technique that significantly reduces the number of elemental gates to build quantum circuits. This is impactful for the design of quantum circuits, and we show below this could reduce the number of gates by 60% and 46% for the four- and five-qubit Toffoli gates, two key quantum circuits, respectively, as compared with simplest known decomposition. Reduced circuit complexity often goes hand-in-hand with higher efficiency and bandwidth. The quantum circuit optimization technique proposed in this work would provide a significant step forward in the optimization of quantum circuits and quantum algorithms, and has the potential for wider application in quantum computation.

Saleem Mohammed Ridha Taha

Bao-nan WANG, Yuhang Chen, Bao YIN +3 more

The small Qubit quantum algorithm attack to RSA was proposed,the need Qubit of the first quantum register from 2L to L1,it can be reduced to 2 Qubit,the overall space complexity denoted (L1,L),where 2L1≥r,r is the period of decomposed.Because of the reduce of the first quantum register,it reduces the algorithm’s complexity and success rates,and use the binary look-up table method to compute the modular exponentiation,it enhances the computing speed.The improved algorithm’s quantum circuit complexity is T=O(2L2).It have a significant improvement on the time complexity and space complexity.Although the success rate is reduced,the overall success solution time is still lower than the Shor algorithm and the current major improvements Shor algorithm.Completed a simulation experiment.Respectively use the 11、10、9 Qubit decomposing the quantum circuit 119.The new algorithm explore the reality of using a universal quantum computer device to decipher the public key cryptography.

Shuichi Hirahara, François Le Gall

Recently Brakerski, Christiano, Mahadev, Vazirani and Vidick (FOCS 2018) have shown how to construct a test of quantumness based on the learning with errors (LWE) assumption: a test that can be solved efficiently by a quantum computer but cannot be solved by a classical polynomial-time computer under the LWE assumption. This test has lead to several cryptographic applications. In particular, it has been applied to producing certifiable randomness from a single untrusted quantum device, self-testing a single quantum device and device-independent quantum key distribution. In this paper, we show that this test of quantumness, and essentially all the above applications, can actually be implemented by a very weak class of quantum circuits: constant-depth quantum circuits combined with logarithmic-depth classical computation. This reveals novel complexity-theoretic properties of this fundamental test of quantumness and gives new concrete evidence of the superiority of small-depth quantum circuits over classical computation.