The National Academies Press

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Pages 30-44

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From page 30... ... In particular, he added, "it has been a workhorse for a long time in quantum sensing and quantum information." For use in measuring magnetic fields in a diamond anvil cell, the key features of NV centers is that they are sensitive to local magnetic fields, which are controlled and read out optically, and they operate in a wide range of temperatures (from millikelvin to hundreds of degrees Kelvin) and pressures (from ambient pressure to at least 170 GPa) Read the entire page →
From page 31... ... However, if the sample is superconducting, then it will expel magnetic fields, and the magnetic fields across the nearby NV centers will be suppressed. Laumann illustrated how this works by showing two images created from a sample of the superconductor bismuth strontium calcium copper oxide (BSCCO) Read the entire page →
From page 32... ... magnetic field was only 50 G, indicating a Meissner effect within the sample. At the same temperature, the resistance dropped sharply as well. Read the entire page →
From page 33... ... QUANTUM STATES IN SEMICONDUCTORS David Awschalom, the Liew Family Professor of Molecular Engineering and vice dean for research and infrastructure at the University of Chicago's Pritzker School of Molecular Engineering, spoke about developing semiconductor qubits for communication and sensing, controlling and extending the spin coherence of NV centers, and also using chemistry to mimic what has been done in solid-state systems to engineer tunable, portable, scalable qubits. "These are really new direc tions," he said, "and it's really fun to share them with you." As context, he said that the overall goal was to take advantage of the tremen dous amount of technological development that has gone into semiconductors and use it for quantum applications. Read the entire page →
From page 34... ... "It's very popular in space technolo gies and avionics," he said, "as basically silicon that works at high temperature." Another advantage is that if one made silicon carbide qubits analogous to the NV center qubits in diamond, the silicon carbide qubits would emit photons at near telecom wavelengths, so they could easily be built into networks. As an example of the sorts of quantum properties that can be built into silicon carbide, Awschalom showed data on quantum spin states taken from a single electron in a commercial 4-inch silicon carbide wafer. Read the entire page →
From page 35... ... This is possible because one can tune the quantum states based on electrical gain. One of the surprises they found when testing the device was its stability, he added. Read the entire page →
From page 36... ... Vanadium produces light at the telecom O-band1 frequency for communication, or at 1.3 microns. The vanadium defects in the silicon carbide produced single photons in the O-band, but different isotopes of vanadium pro duced photons with slightly different frequencies; that is, he elaborated, the optical emissions from these states can resolve a single additional neutron in an atom, and each neutron produces a 20 GHz energy shift. Read the entire page →
From page 37... ... The nanocrystals have organic ligands attached to their surfaces, and the spins of the erbium atoms in a crystal are coupled to hydrogen atoms on the ligands. The researchers did not shield the nanocrystals from Earth's magnetic field, and they observed the erbium qubits in the nanocrystals "beating" because of the coupling with the hydrogen atoms in the presence of the magnetic field. Read the entire page →
From page 38... ... "So it seemed to us that ensembles would be pretty interesting, because, essentially, it's an array of atoms." He had naively thought, he said, that a single molecule would offer a good approach, "but then the coupling coefficients seemed to be an issue with the superconducting qubits." His team has been think ing about both. DISCUSSION Narang began the panel discussion by noting that, with the exception of wschalom's talk, most of the platforms that had been discussed to that point were A not designed for use in telecommunications and then asking how important is it that these various networks operate in telecommunications frequencies. Read the entire page →
From page 39... ... One could imagine, he said, applying a gradient magnetic field or gradient electric field to an array of qubits so that one could distinguish small ensembles of qubits, if not actually an individual qubit. There is not yet a proof of concept, though, he added. Read the entire page →
From page 40... ... The limiting factor in working with atoms of various materials that one could use in a technology is the ability to control and operate them, he said. "The coherence time is what hap pens during free evolution, but with quantum computing and other technologies, what's really important is what happens during driven evolution," he explained. Read the entire page →
From page 41... ... "They're on a plane or on a vehicle. They're shaking and all that." This raises various engineering challenges, he added, "but I find it very exciting that we're actually using quantum sensing to do some of this work now." Dimitri Green from Boston University asked Oliver if he could use his systems to simulate atoms or other fermionic systems. Read the entire page →
From page 42... ... OPTICAL CAVITIES James Thompson of the University of Colorado Boulder and JILA described various ways that he uses optical cavities to study quantum properties, including entanglement and coherence. Specifically, he said, his laboratory focuses on harnessing light–matter interactions for quantum simulation and sensing. Read the entire page →
From page 43... ... "We're not trying to get down to one atom," he said. "We want collective physics." One of the key parameters in their experiments is the cooperativity parameter, C, which Thompson described as, in the case of a single atom inside the optical cavity, the ratio of how much the atom "talks to" the cavity mode versus how much it talks to all the other modes of free space. Read the entire page →
From page 44... ... SOURCE: James Thompson, University of Colorado Boulder and JILA, presentation to the workshop, October 3, 2024. Read the entire page →

From page 30...

... In particular, he added, "it has been a workhorse for a long time in quantum sensing and quantum information." For use in measuring magnetic fields in a diamond anvil cell, the key features of NV centers is that they are sensitive to local magnetic fields, which are controlled and read out optically, and they operate in a wide range of temperatures (from millikelvin to hundreds of degrees Kelvin) and pressures (from ambient pressure to at least 170 GPa)