The Loss–DiVicenzo quantum computer proposal tried to fulfill DiVincenzo's criteria for a scalable quantum computer,[11] namely:
identification of well-defined qubits;
reliable state preparation;
low decoherence;
accurate quantum gate operations and
strong quantum measurements.
A candidate for such a quantum computer is a lateral quantum dot system. Earlier work on applications of quantum dots for quantum computing was done by Barenco et al.[12]
Implementation of the two-qubit gateedit
The Loss–DiVincenzo quantum computer operates, basically, using inter-dot gate voltage for implementing swap operations and local magnetic fields (or any other local spin manipulation) for implementing the controlled NOT gate (CNOT gate).
The swap operation is achieved by applying a pulsed inter-dot gate voltage, so the exchange constant in the Heisenberg Hamiltonian becomes time-dependent:
This description is only valid if:
the level spacing in the quantum-dot is much greater than
the pulse time scale is greater than , so there is no time for transitions to higher orbital levels to happen and
We can choose a specific duration of the pulse such that the integral in time over gives and becomes the swap operator
This pulse run for half the time (with ) results in a square root of swap gate,
The "XOR" gate may be achieved by combining operations with individual spin rotation operations:
The operator is a conditional phase shift (controlled-Z) for the state in the basis of .[2]: 4 It can be made into a CNOT gate by surrounding the desired target qubit with Hadamard gates.
^D. P. DiVincenzo, in Mesoscopic Electron Transport, Vol. 345 of NATO Advanced Study Institute, Series E: Applied Sciences, edited by L. Sohn, L. Kouwenhoven, and G. Schoen (Kluwer, Dordrecht, 1997); on arXiv.org in Dec. 1996
^Barenco, Adriano; Deutsch, David; Ekert, Artur; Josza, Richard (1995). "Conditional Quantum Dynamics and Logic Gates". Phys. Rev. Lett. 74 (20): 4083–4086. arXiv:quant-ph/9503017. Bibcode:1995PhRvL..74.4083B. doi:10.1103/PhysRevLett.74.4083. PMID 10058408. S2CID 26611140.
External linksedit
QuantumInspire online platform from Delft University of Technology, allows building and running quantum algorithms on "Spin-2" a 2 silicon spin qubits processor.