Superconducting and Spin-based Qubits
Illustration depicting spins coupled by interaction and being able to perform coherent rotations.
Our research is devoted to both the theoretical and experimental aspects of quantum computing with superconducting or spin qubits. The perspective of having quantum computers performing calculations at unparalleled speeds is attractive and challenging for both the pure scientist and the engineer. Quantum bits, or qubits, are the elementary units of a quantum computer and are described using a set of two states, |0> and |1>. Due to its quantum nature, a qubit can exist in states spanning any superposition of the two set functions, whereas its classical analog can be either 0 or 1. Consequently, an operation on one qubit causes simultaneous operations on each of the combination's components, which can be used to speed up certain kinds of calculations. Likewise, a single operation on a multi-qubit system can affect a huge amount of information, compared with just changing a single bit from 0 to 1.
As solid-state qubits, superconducting systems are very appealing since they have mesoscopic sizes and can be elaborated in clean rooms on tiny chips. They show relatively large coherence times, of the order of tenth of microseconds and are generally described by a two-level Hamiltonian. Electronic spins in various systems can be used as qubits as well, one example being quantum dots containing one free electron. Of special interest to our research are molecules formed of magnetic ions (V, Fe, Mn, etc) strongly coupled by exchange and acting as a single spin or systems showing diluted spins in non-magnetic matrices. Though in crystalline form, the spins are relatively well isolated from each other and thus their quantum physics is not strongly affected by the collective nature of the sample. In diluted spin systems, quantum coherence can be preserved up to room temperature, making these systems suitable candidates as quantum bits.
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For more information, contact Nicholas Bonesteel (theory) or Irinel Chiorescu (experiment).
