New Room Temperature Solid-State Qubits for Future Quantum Computers. S. Nellutla, K.-Y. Choi, M. Pati, J. van Tol, I. Chiorescu and N. S. Dalal NHMFL, Dept. of Chemistry and Biochemistry and Dept. of Physics, FSU.
S. Nellutla, K.-Y. Choi, M. Pati, J. van Tol, I. Chiorescu and N. S. Dalal
NHMFL, Dept. of Chemistry and Biochemistry and Dept. of Physics, FSU
Current semiconductor computer technology is slowly reaching its limits of performance. The new magic term for future alternatives is “quantum computing”, where we enter the fascinating realm of quantum mechanics, and of quantized properties of materials.
In a classical computer information is stored in bits, and can have the value of 0 or 1. In a quantum computer on the other hand,quantum bits (qubits) are the elementary units and they are described using a set of two quantum wavefunctions, |0> and |1>. Due to its quantum nature, a qubit can exist in any superposition of |0> and |1> and thus can have an infinite number of possible states instead of just 1 or 0. Coherence, the ability to maintain such superpositions, is the name of the game for scientists in this field. Quantum signatures which are easily recognizable in atomic systems in gaseous state are significantly harder to be obtained in solid state systems because the interactions with the environment can change the state of the qubit, leading to the wrong answer.
In this study we introduce a new solid state material in which qubit interaction
with their local environment, mostly neighboring nuclear spins, can be suppressed
to such an extent that quantum superpositions are detectable even at room
temperature. Starting from solution, single crystals of K3NbO8 doped with Cr5+ have
been obtained. Cr atoms carry a spin with projection ±1/2 defining the two qubit
states. Rabi oscillations are observed for the first time in a spin system based on transition metal oxides up to room temperature. At liquid helium temperature the phase coherence relaxation time T2 reaches ~ 10 μs and, with a Rabi frequency of 20 MHz, yields a single qubit figure of merit of about 500. This shows that a diluted ensemble of Cr5+ doped K3NbO8 is a potential candidate for solid-state quantum information processing.
Crystalline structure of Cr doped K3NbO8 with only electronic spins
S=1/2 at Cr sites. Pulsed temporal variations of local electromagnetic
field (suggested in black) are used to control the quantum
superposition of the two spin states known as |0> and |1>. The
background shows measured Rabi oscillations (between states |0>
and |1>) at 4K.
S. Nellutla, K.-Y. Choi, M. Pati, J. van Tol, I. Chiorescu and N. S. Dalal, Coherent Manipulation of Electron Spins up to Ambient
Temperatures in Cr5+ Doped K3NbO8, Phys. Rev. Lett. in press (2007)