Another Step Forward on Universal Quantum Computer.
This is a nitrogen-vacancy (NV) center in diamond with two crossed wires for holonomic quantum gates over the geometric spin qubit with a polarized microwave.
Researchers have demonstrated holonomic quantum gates under zero-magnetic field at room temperature which will enable the realization of fast and fault-tolerant universal quantum computers.
A quantum computer is a powerful machine with the potential to solve complex problems much faster than today’s conventional computer can. Researchers are currently working on the next step in quantum computing: building a universal quantum computer.
Experimental demonstration of non-adiabatic and non-abelian holonomic quantum gates over a geometric spin qubit on an electron or nitrogen nucleus which paves the way to realizing a universal quantum computer.
The geometric phase is currently a key issue in quantum physics. A holonomic quantum gate manipulating purely the geometric phase in the degenerate ground state system is believed to be an ideal way to build a fault-tolerant universal quantum computer. The geometric phase gate or holonomic quantum gate has been experimentally demonstrated in several quantum systems including nitrogen-vacancy (NV) centers in diamond. However previous experiments required microwaves or light waves to manipulate the non-degenerate subspace leading to the degradation of gate fidelity due to unwanted interference of the dynamic phase.
“To avoid unwanted interference, we used a degenerate subspace of the triplet spin qutrit to form an ideal logical qubit which we call a geometric spin qubit in an nitrogen-vacancy (NV) center. This method facilitated fast and precise geometric gates at a temperature below 10 K and the gate fidelity was limited by radiative relaxation” says X Professor Georgian Technical University. “Based on this method in combination with polarized microwaves we succeeded in manipulation of the geometric phase in an nitrogen-vacancy (NV) center in diamond under a zero-magnetic field at room temperature”.
The group also demonstrated a two-qubit holonomic gate to show universality by manipulating the electron-nucleus entanglement. The scheme renders a purely holonomic gate without requiring an energy gap which would have induced dynamic phase interference to degrade the gate fidelity and thus enables precise and fast control over long-lived quantum memories for realizing quantum repeaters interfacing between universal quantum computers and secure communication networks.