New-Tech Europe Magazine | Q3 2021 | Digital Edition

access to both the electron and the (nitrogen) nuclear spins offers many advantages as they fulfill different functions. Electron spins have shorter coherence times but offer a fast control, while more stable nuclear spins could be used, for example, as a memory qubit to store spin information from the electronic qubit. The two types of qubits can also be entangled. Entanglement is an essential quantum process enabling quantum computers, it cuts down the information transfer time between qubits and is ultimately necessary for many other quantum applications such as quantum communication. So far, devices using quantum entanglement work mainly at ultra-low temperatures, close to absolute 0K. Electrical readout at room temperature Currently, the entanglement of a nuclear and electron spin is read out optically with bulky setups. Milos Nesladek: “We are interested in reading the spins states electrically, because it would open access to miniaturization and integration of electronic devices with several entangled modular electron-nuclear spin units on a single electronic quantum chip. These units can communicate in two ways. Firstly, one can place them close to each other, typically at less than 50nm, but then they cannot be resolved optically due to the diffraction-limit of optics. This poses a problem for operating the units individually and for using entangling quantum gates. To circumvent this, we fabricated electrical contacts around the NV centers in the units, which allows the units to be read individually.” “With an electrical readout, the

Figure 1: The optical table with a room temperature quantum microscope setup used in the single nuclear spin readout experiment.

spatial resolution is solely determined by the electrode size which opens the way to placing spin-qubits in close proximity and ultimately to fabricate nanoscale quantum systems with semiconductor scalability. It has

been successfully used to measure the spin state of large ensembles of nuclear spins recently, but fundamental quantum operations rely on the driving and readout of single qubits. Here, we show the

Figure 2: Details showing guiding of the 532nm laser beam used for NV spin polarization and readout. The beam is directed onto the quantum chip consisting of a diamond plate equipped with electrical contacts and MW strip lines for spin state manipulation (not shown).

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