Measurement of the optically induced spin polarisation of N-V centres in diamond

Harrison, Joanne; Sellars, Matthew; Manson, Neil B.

doi:10.1016/j.diamond.2005.12.027

Cited by 91 publications

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“…This is consistent with the preferred spin orientation established experimentally [24]. With these selection rules, assuming the optical induced spin polarization is faster than spin-lattice relaxation, the spin polarization would be 100% but this is not what is observed [25].…”

Section: Nitrogen-vacancy Centersupporting

confidence: 74%

“…As in the model we take k sx = k sy = 0. In a recent paper we have reported that the maximum spin polarization obtained for an ensemble under continuous excitation is 80% [25]. This means that the probability of optically transferring spin projection from the z spin state to an x, y spin is 1/4 of the above process giving rise to the spin polarization.…”

Section: Relaxation and Inter-system Decay Ratesmentioning

confidence: 99%

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Nitrogen-vacancy center in diamond: Model of the electronic structure and associated dynamics

2006

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Symmetry considerations are used in presenting a model of the electronic structure and the associated dynamics of the nitrogen-vacancy center in diamond. The model accounts for the occurrence of optically induced spin polarization, for the change of emission level with spin polarization and for new measurements of transient emission. The rate constants given are in variance to those reported previously.

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Section: Nitrogen-vacancy Centersupporting

confidence: 74%

Section: Relaxation and Inter-system Decay Ratesmentioning

confidence: 99%

Nitrogen-vacancy center in diamond: Model of the electronic structure and associated dynamics

2006

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“…1(b)]. T 1 for both the N-V and N centers was measured from room temperature to 40 K. Below 40 K, where T 1 is longer than tens of seconds [29,30], an accurate measurement with the current setup proved impractical as the drift of the superconducting magnet ( 5 ppm=h) becomes nontrivial on the timescale of the measurement. T 1 is obtained by fitting a decay exponential to the recovery rate of the echo area y 0 ÿ ae ÿT=T 1 .…”

Section: Prl 101 047601 (2008) P H Y S I C a L R E V I E W L E T T Ementioning

confidence: 99%

Quenching Spin Decoherence in Diamond through Spin Bath Polarization

et al. 2008

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We experimentally demonstrate that the decoherence of a spin by a spin bath can be completely eliminated by fully polarizing the spin bath. We use electron paramagnetic resonance at 240 GHz and 8 T to study the electron-spin coherence time T 2 of nitrogen-vacancy centers and nitrogen impurities in diamond from room temperature down to 1.3 K. A sharp increase of T 2 is observed below the Zeeman energy (11.5 K). The data are well described by a suppression of the flip-flop induced spin bath fluctuations due to thermal electron-spin polarization. T 2 saturates at 250 s below 2 K, where the polarization of the electron-spin bath exceeds 99%. DOI: 10.1103/PhysRevLett.101.047601 PACS numbers: 76.30.Mi, 03.65.Yz Overcoming spin decoherence is critical to spintronics and spin-based quantum information processing devices [1,2]. For spins in the solid state, a coupling to a fluctuating spin bath is a major source of the decoherence. Therefore, several recent theoretical and experimental efforts have aimed at suppressing spin bath fluctuations [3][4][5][6][7][8][9]. One approach is to bring the spin bath into a well-known quantum state that exhibits little or no fluctuations [10,11]. A prime example is the case of a fully polarized spin bath. The spin bath fluctuations are fully eliminated when all spins are in the ground state. In quantum dots, nuclear spin bath polarizations of up to 60% have been achieved [12,13]. However, a polarization above 90% is needed to significantly increase the spin coherence time [14]. Moreover, thermal polarization of the nuclear spin bath is experimentally challenging due to the small nuclear magnetic moment. Electron-spin baths, however, may be fully polarized thermally at a few degrees of Kelvin under an applied magnetic field of 8 T.Here we investigate the relationship between the spin coherence of nitrogen-vacancy (N-V) centers in diamond and the polarization of the surrounding spin bath consisting of nitrogen (N) electron spins. N-V centers consist of a substitutional nitrogen atom adjoining to a vacancy in the diamond lattice. The N-V center, which has long spin coherence times at room temperature [15,16], is an excellent candidate for quantum information processing applications as well as conducting fundamental studies of interactions with nearby electronic spins [16 -18] and nuclear spins [19,20]. In the case of type-Ib diamond, as studied here, the coupling to a bath of N electron spins is the main source of decoherence for an N-V center spin [15,21]. We have measured the spin coherence time (T 2 ) and spin-lattice relaxation time (T 1 ) in spin ensembles of N-V centers and single N impurity centers (P1 centers) using pulsed electron paramagnetic resonance (EPR) spectroscopy at 240 GHz. By comparing the values of T 1 and T 2 at different temperatures, we verify that the mechanism determining T 2 is different from that of T 1 . Next, we investigate the temperature dependence of T 2 .At 240 GHz and 8.6 T where the Zeeman energy of the N centers corresponds to 11.5 K, the polariza...

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“…These polarizations and number of controllable qubits are within reach in a variety of electron-nuclear systems [28,29]. For example, nitrogen vacancy electronic centers in diamond can be optically pumped to ∼ 80% [30], or the thermal bias of electron spins (g ≈ 2) at cryogenic temperatures and typical fields of a few Tesla provides sufficient polarization.…”

Section: Figmentioning

confidence: 99%

Spin Based Heat Engine: Demonstration of Multiple Rounds of Algorithmic Cooling

et al. 2008

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We show experimental results demonstrating multiple rounds of heat-bath algorithmic cooling in a 3 qubit solid-state nuclear magnetic resonance quantum information processor. By dynamically pumping entropy out of the system of interest and into the heat-bath, we are able show purification of a single qubit to a polarization 1.69 times that of the heat-bath and thus go beyond the Shannon bound for closed system cooling. The cooling algorithm implemented requires both high fidelity coherent control and a deliberate controlled interaction with the environment. We discuss the improvements in control that allowed this demonstration. This experimental work shows that given this level of quantum control in systems with sufficiently large polarizations, nearly pure qubits should be achievable. Using quantum mechanics to process information promises the possibility to dramatically speed-up certain computations and simulations [1]. Many experimental paths are being pursued in the goal of coherently manipulating quantum systems [2]. The standard circuit based model has certain experimental criteria [3]: one of which is the ability to initialize pure fiducial quantum states. This is needed not only to create the initial state for many quantum algorithms, but it is also necessary to have pure qubits on demand throughout the computation in order to compute fault-tolerantly in the presence of errors [4]. However, many physical implementations are able to initialize only mixed states with a certain bias towards the desired state. In these cases it will almost certainly be necessary to run some protocol to purify the qubits. Aside from quantum information purposes, the ability to increase the bias of nuclear spins is fundamentally important in nuclear magnetic resonance (NMR) where small signal to noise ratios are usually overcome with signal averaging. A boost in the initial bias by a factor b would reduce the experiment time by b 2 .A potential solution is algorithmic, whereby a series of logic gates can lower the temperature of a subset of the qubits. If the relaxation rate back to thermal equilibrium (T 1 ) is sufficiently longer than the cooling operations, then it is possible to cool a subset far below their thermal equilibrium bias. This algorithmic cooling is essentially classical and is based on early work from von Neumann [5]. If the bits start with some bias ǫ, so the probability of being in the state 0 or spin up is P ↑ = 1+ǫ 2 and P ↓ = 1−ǫ 2 , then the application of a logic gate can compress the uncertainty into some fraction of the qubits and increase the bias on the rest. Using these ideas it was shown that by starting with a sufficient number of qubits, it is possible to initialize a small number of qubits to a fiducial state with near certainty [6,7]. However, for the starting biases typical of room temperature NMR, that sufficient number is an impractically large number e.g., to purify only one qubit requires ≈ 10 12 spins. In a closed system, the compression step is limited by the Shannon bound: the total en...

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Measurement of the optically induced spin polarisation of N-V centres in diamond

Cited by 91 publications

References 0 publications

Nitrogen-vacancy center in diamond: Model of the electronic structure and associated dynamics

Nitrogen-vacancy center in diamond: Model of the electronic structure and associated dynamics

Quenching Spin Decoherence in Diamond through Spin Bath Polarization

Spin Based Heat Engine: Demonstration of Multiple Rounds of Algorithmic Cooling

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