Publications & Patents
Dr. Suzanne Gildert is a prolific inventor, technologist and scientific author regarding quantum computing, humanoid robotics and artificial general intelligence. She is named as an inventor on 67 filed U.S. patents, many of which are also listed on Google Patent. Her PhD thesis, βMacroscopic quantum tunnelling effects in Josephson junctions,β explored the quantum effects of superconducting components in quantum computers.
Many interesting but practically intractable problems can be reduced to that of finding the ground state of a system of interacting spins; however, finding such a ground state remains computationally difficult. It is believed that the ground state of some naturally occurring spin systems can be effectively attained through a process called quantum annealing. If it could be harnessed, quantum annealing might improve on known methods for solving certain types of problem.
However, physical investigation of quantum annealing has been largely confined to microscopic spins in condensed-matter systems. Here we use quantum annealing to find the ground state of an artificial Ising spin system comprising an array of eight superconducting flux quantum bits with programmable spinβspin couplings. We observe a clear signature of quantum annealing, distinguishable from classical thermal annealing through the temperature dependence of the time at which the system dynamics freezes. Our implementation can be configured in situ to realize a wide variety of different spin networks, each of which can be monitored as it moves towards a low-energy configuration. This programmable artificial spin network bridges the gap between the theoretical study of ideal isolated spin networks and the experimental investigation of bulk magnetic samples. Moreover, with an increased number of spins, such a system may provide a practical physical means to implement a quantum algorithm, possibly allowing more-effective approaches to solving certain classes of hard combinatorial optimization problems.
Efforts to develop useful quantum computers have been blocked primarily by environmental noise. Quantum annealing is a scheme of quantum computation that is predicted to be more robust against noise, because despite the thermal environment mixing the systemβs state in the energy basis, the system partially retains coherence in the computational basis, and hence is able to establish well-defined eigenstates.
Here we examine the environmentβs effect on quantum annealing using 16 qubits of a superconducting quantum processor. For a problem instance with an isolated small-gap anticrossing between the lowest two energy levels, we experimentally demonstrate that, even with annealing times eight orders of magnitude longer than the predicted single-qubit decoherence time, the probabilities of performing a successful computation are similar to those expected for a fully coherent system. Moreover, for the problem studied, we show that quantum annealing can take advantage of a thermal environment to achieve a speedup factor of up to 1,000 over a closed system.
We report measurements of macroscopic resonant tunneling between the two lowest energy states of a pair of magnetically coupled rf-superconducting quantum interference device flux qubits. This technique provides both a direct means of measuring the energy gap of the two-qubit system and a method for probing of the environment coupled to the pair of qubits. Measurements of the tunneling rate as a function of qubit flux bias show a Gaussian line shape that is well matched to theoretical predictions. Moreover, the peak widths indicate that each qubit is coupled to a local environment whose fluctuations are uncorrelated with that of the other qubit.
We have measured the resistance vs temperature, π β‘(π), and current vs voltage, πΌβ‘(π), for a series of submicrometer Yβ’Ba2β’Cu3β’O7βπΏ tracks. We find that superconductivity is suppressed when the room temperature resistance is greater than the superconducting resistance quantum, π π=β/4β’πΒ². In addition, we observe regular steps in the πΌβ‘(π) characteristics of some bridges, which we associate with phase slip centers. For one bridge, with resistance just below the resistance quantum, π π, we find a gradual entry into the superconducting state which is well fit by theoretical predictions for thermally activated phase slips in a superconducting wire.
We have measured the resistance vs temperature, π β‘(π), and current vs voltage, πΌβ‘(π), for a series of submicrometer Yβ’Ba2β’Cu3β’O7βπΏ tracks. We find that superconductivity is suppressed when the room temperature resistance is greater than the superconducting resistance quantum, π π=β/4β’πΒ². In addition, we observe regular steps in the πΌβ‘(π) characteristics of some bridges, which we associate with phase slip centers. For one bridge, with resistance just below the resistance quantum, π π, we find a gradual entry into the superconducting state which is well fit by theoretical predictions for thermally activated phase slips in a superconducting wire.
