Room-temperature manipulation and decoherence of a single spin in diamond

Abstract

We report on room-temperature coherent manipulation of the spin of a single nitrogen-vacancy center in diamond and a study of its coherence as a function of magnetic field. We use magnetic resonance to induce Rabi nutations, and apply a Hahn spin echo to remove the effect of low-frequency dephasing. A sharp rise in the decoherence rate is observed at magnetic fields where the nitrogenvacancy center spin couples resonantly to substitutional nitrogen spins via the magnetic dipolar coupling. Finally, we find evidence that away from these energy resonances spin flips of nitrogen electrons are the main source of decoherence.PACS numbers: 76.30. Mi,03.67.Lx,03.65.Yz The study of single quantum systems is interesting both for testing fundamental laws of physics as well as for practical purposes, as computing with quantum systems promises an enormous increase in computing power and quantum communication allows secure information exchange 1 . In the solid state, coherent control of single quantum systems has been achieved in a number of systems, e.g. superconducting Cooper pair boxes 2 and electron spins in quantum dots 3 . Among these, the nitrogenvacancy (N-V) center in diamond 4 is unique, because its spin exhibits a long coherence time that persists up to room-temperature 5 , whereas most other systems only allow coherent control at cryogenic temperatures.Coherent manipulation of N-V centers on large ensembles was first achieved many years ago 6,7 . Recently, however, coherent rotations and spin echoes of a single N-V center spin were reported by Jelezko et al. 8 . This landmark experiment, that has not been reproduced by a different group thus far, demonstrates that the N-V center provides a testbed for quantum manipulation in the solid state at room temperature 9,10 . On the other hand, single-center spectroscopy allows the study of the local environment of the N-V center 11 and has already unveiled anisotropic spin interactions and magnetic dipolar coupling to spins of other defects in diamond 12 . Recent results of these studies include the observation of strong coupling between a single N-V center and the spin of a single substitutional nitrogen atom 13,14 and the measurement of the spin relaxation time of a single nitrogen electron spin 14 . By combining single-center spectroscopy with coherent control, the coherent interaction of the N-V center spin with its environment can be probed, which might ultimately lead to coherent quantum circuits 9 .Here, we report coherent control of the electron spin state of a single N-V center at room temperature. We demonstrate that we can coherently drive single-spin rotations (Rabi nutations) and undo low-frequency dephasing by application of a Hahn spin echo sequence. We use this capability to study the coherence of the N-V center as a function of applied magnetic field. By comparing the magnetic-field dependences of the decoherence rate and the photoluminescence, we find that the coherence of the N-V center spin is strongly affected by the resonant spin exchange with the...

Coherent spin control of a nanocavity-enhanced qubit in diamond

“…Separate Rabi oscillation measurements (Fig. 4c) under pulsed excitation indicate a Rabi envelope decay time 16 of T 0 2 46 ms. (Please refer to Supplementary Fig. 3 and Supplementary Note 3 for T 1 measurements.)…”

“…3 and Supplementary Note 3 for T 1 measurements.) The phase coherence time F 2 is measured using a Hahn echo to cancel the dephasing by quasi-static magnetic fields 16 . From the singleexponential 17 decay envelope of the revivals in Fig.…”

Spins in few-electron quantum dots

“…These two-and three-electron qubit encodings eliminate the need for the technologically challenging single-spin rotations. Many more variations for encoding qubits in several electron spins have been proposed, each having its own advantages and drawbacks ͑Byrd and Lidar, 2002;Lidar, 2002a, 2002b;Meier et al, 2003;Kyriakidis and Penney, 2005;Taylor et al, 2005;Hanson and Burkard, 2007͒. In the end, the best implementation for a given system will depend on many factors that are hard to oversee at this stage.…”

“…The most well-known approach is electron spin resonance ͑ESR͒, whereby a rotating magnetic field B 1 is applied perpendicularly to the static field B along ẑ , and on-resonance with the spin-flip transition energy ͑f ac = g B B / h͒, as illustrated in Fig. 41 Rugar et al, 2004;Xiao et al, 2004;Hanson et al, 2006͒, including in a quantum dot ͑Kop-pens et al, 2006͒. In addition, the free precession of an electron spin in a quantum dot has been observed with optical techniques ͑Dutt et al, 2005; The quantum dot ESR experiment was realized by Koppens et al ͑2006͒, and is inspired by the idea of Engel and Loss to tune a single quantum dot to Coulomb blockade with the electrochemical potential alignment as shown in Fig.…”

“…Therefore we focus on single and coupled quantum dots containing only one or two electrons. These systems are particularly important as they constitute the building blocks of proposed electron spin-based quantum information processors ͑Loss and DiVincenzo, 1998;DiVincenzo et al, 2000;Byrd and Lidar, 2002;Levy, 2002;Lidar, 2002a, 2002b;Meier et al, 2003;Kyriakidis and Penney, 2005;Taylor et al, 2005;Hanson and Burkard, 2007͒.…”