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From page 14... ... The second example was the Haah cubic code for a model in three dimensions, which provides a different type of quantum error correcting code that is more robust than the toric code. "But it also has been really interesting for condensed matter physicists," Khemani said, "because it gives you an exotic type of phase called a fracton phase." Much rich physics has come out of studying phases like this, she said. Read the entire page →
From page 15... ... How does quantum information scramble across the entire system? When subsystems come to thermal equilibrium, all information about the initial state is preserved for all times, but it can get very scrambled. Read the entire page →
From page 16... ... Measurements, she said, "can create, destroy, and restructure quantum correlations, and this can allow you to get new types of non-equilibrium phases driven by how these measurements are behaving." As a third example, she pointed to work from the Google Quantum AI group where they observed measurement-induced phase transitions in individual quantum trajectories labeled by controlled measurements. The work involved a new type of error-correcting code called the Hastings-Haah-Floquet code, generated by a periodic sequence of local measurements with some particular symmetries and structure. Read the entire page →
From page 17... ... Khemani added that one way in which the current work on coherent quantum networks has relevance for real materials is through the back-and-forth between theory and experimentation. When physicists want to understand some very complex phenomena, they will often model it with some "toy system" that captures much of the physics. Read the entire page →
From page 18... ... "How smart do you want the end nodes to be, versus somewhere in the middle, which would be essentially asking, do you want to put quantum processors in every city, as opposed to in 10 cities? " In response to an audience question about practical limits to scaling the sorts of coherent quantum networks being discussed, Marcus said that he has not been able to get the networks to work with high-temperature superconductors, so it is still necessary to cool the devices down to near absolute zero rather than to the 77 K of liquid nitrogen. Read the entire page →
From page 19... ... Marcus spoke of the example of superconductors and Bardeen–Cooper– Schrieffer theory. It is a mean field theory, so the entanglement is hidden, but that is different from saying the entanglement is absent, he said. Read the entire page →
From page 20... ... 1983. "Josephson-Junction Arrays in Transverse Magnetic Fields." Physical Review Letters 51(21) Read the entire page →
From page 21... ... , who spoke virtually, described his work in emulating Bose–Hubbard models with arrays of superconducting qubits. He began with a brief overview of the different types of quantum simulation, ranging from natural materials to simulators. Read the entire page →
From page 22... ... Gustavsson, and W.D. Oliver, 2019, "A Quantum Engineer's Guide to Superconducting Qubits," Applied Physics Reviews 6(2) Read the entire page →
From page 23... ... Muschinske, C Barrett, et al., 2024, "A Synthetic Magnetic Vector Potential in a 2D Superconducting Qubit Array," Nature Physics 20:1881–1887. Read the entire page →
From page 24... ... Among the other experiments the team has carried out on 9- and 16-qubit chips are work with out-of-time-ordered correlation functions, studies of area ver sus volume law entanglement, and work with quantum attention networks. But for his presentation, Oliver focused on two particular examples more closely aligned with the topic of the workshop -- work on Anderson and Stark localization with Bloch oscillations and on synthetic magnetic vector potential. Read the entire page →
From page 25... ... The average readout fidelity is 93 percent, and the aver age randomized benchmarking fidelity is 99.8 percent for individual qubits and 99.6 percent for simultaneous qubits. Synthetic Magnetic Vector Potential There are many examples of physics that one would want to emulate that re quire magnetic fields, such as quantized Hall states, topological superconductivity, the Hall effect, weak localization, and the anomalous Hall effect. Read the entire page →
From page 26... ... Oliver then offered a number of examples of the sorts of experiments that can be done on the arrays of superconducting qubits with such a synthetic magnetic vector potential added. In the first, carried out in a square of 4 qubits, he demon strated the effects of turning on the synthetic magnetic vector potential by apply ing a Peierls phase of π between 2 qubits. Read the entire page →
From page 27... ... Finally, Oliver described how his team used the synthetic magnetic vector po tential to emulate flat bands in one dimension. They strung together 2 × 2 plaquettes to emulate three-unit cells of the rhombus lattice, which always features one flat band in its band structure (Figure 3-4) Read the entire page →
From page 28... ... centers in diamonds as a tool for probing the properties of superconductors in diamond anvil cells. He commented that his talk would include much about quantum materials, it would have very little to do with networks. Read the entire page →
From page 29... ... It is possible to get to 100 or even 200 GPa with just some screws, Laumann said. With these pressures, the hydrides of interest can be created inside the diamond anvil cell, but they are not stable and will transform into a dif ferent phase if removed from the cell. Read the entire page →

From page 14...

... The second example was the Haah cubic code for a model in three dimensions, which provides a different type of quantum error correcting code that is more robust than the toric code. "But it also has been really interesting for condensed matter physicists," Khemani said, "because it gives you an exotic type of phase called a fracton phase." Much rich physics has come out of studying phases like this, she said.