Spin qubit quantum device read by impedance measurement

#The invention refers to the field of quantum electronics and quantum computing. The invention refers more specifically to a quantum device in which the reading of electron spins or holes in quantum wells based on semiconductor technology (GaAs, Silicon, etc.), or qubit readout, is achieved through impedance measurement.

#Quantum computing is based on using a quantum state with two measurable levels as the information vector, referred to as a qubit, and on laws of quantum mechanics (superposition, entanglement, measurement) to execute algorithms. These quantum algorithms have the potential to exceed certain classes of conventional algorithms, for example to perform prime number factorization in the field of cryptography or to solve optimization problems. Regardless of the technology used, a quantum computer comprises several thousand qubits on which three types of operations are performed: initialization of the qubits to a known state, manipulation of the qubits, and readout of the qubits. The implementation of such a quantum computer also requires the setup of error correction codes which need fast, massive and repeated manipulations and readouts on all qubits to prevent information loss.

#Semiconductor technologies are being studied for the construction of qubits, owing to their great integration potential, comparably to conventional electronics. Electrons or holes are individually confined to quantum wells located in a cryostat at cryogenic temperatures (less than 4 K, or even less than 1 K) made within confinement structures on a nano scale defined electrostatically and, in the case of silicon, having an architecture close to that of MOSFETs. The application of a static magnetic field (for example from 100 mT to 1 T) makes it possible to reveal the spin of quasi-particles, which is a quantum system with two measurable levels called “spin down” and “spin up.” Their quantum state is a superposition of these two states represented by the direction of an arrow within a sphere, called a Bloch sphere. The manipulation (rotation) of these spins is done by means of an alternating component of the magnetic field (with a frequency, for example, of between 1 GHz and several tens of GHz) or by means of an alternating electric field at these same frequencies in the case of an adequate spin-orbit interaction (the case of holes in silicon). Reading of the spins (up or down) allows part of the quantum information to be extracted according to its probability of being in each state, determined by the quantum superposition.

#The present invention will be more readily understood from a reading of the description of embodiments, given purely as examples and not intended to limit in any way, in reference to the appended drawings, in which:

#FIG. 1 shows a schematic diagram of the operation of the quantum device;

#FIG. 2 is a schematic diagram of a quantum device according to a first embodiment;

#Identical, similar, or equivalent parts of the various figures described below have the same numerical references so as to facilitate the reading of the various figures.

#In an effort to make the figures more legible, the various parts in the figures are not necessarily shown according to a uniform scale.

#The various possibilities (variants and embodiments) must be understood as not being exclusive of each other, and may therefore be combined.