One-second coherence for a single electron spin coupled to a multi-qubit nuclear-spin environment

Abobeih, Mohamed; Cramer, Julia; Bakker, M.; Kalb, Norbert; Markham, Matthew; Twitchen, Daniel J.; Taminiau, T. H.

doi:10.1038/s41467-018-04916-z

Cited by 265 publications

(294 citation statements)

References 66 publications

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“…We take R = n 2 ; we assume a constant beam-waist w I over the cavity length. Taking a representative value, w 0,I = 0.77 µm (an average of the beam-waist at the top mirror and the minimum beam-waist), we find a maximum | E vac (z)| = 54.4 kV/m inside the diamond from which we can calculate the effective mode volume of a cubic resonator made from diamond to be V eff = 84.9(λ/n) 3 . With the cavity Q-factor on resonance Q c (λ c ) = 8,200, we calculate the Purcell factor to be F P (λ c ) = 1 + 3/(4π 2 ) · Q c /V · (λ/n) 3 · 1/2 = 4.7.…”

Section: Resultsmentioning

confidence: 99%

Cavity-Enhanced Raman Scattering for In Situ Alignment and Characterization of Solid-State Microcavities

et al. 2020

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We report cavity-enhanced Raman scattering from a single-crystal diamond membrane embedded in a highly miniaturized fully-tunable Fabry-Pérot cavity. The Raman intensity is enhanced 58.8fold compared to the corresponding confocal measurement. The strong signal amplification results from the Purcell effect. We show that the cavity-enhanced Raman scattering can be harnessed as a narrowband, high-intensity, internal light-source. The Raman process can be triggered in a simple way by using an optical excitation frequency outside the cavity stopband and is independent of the lateral positioning of the cavity mode with respect to the diamond membrane. The strong Raman signal emerging from the cavity output facilitates in situ mode-matching of the cavity mode to single-mode collection optics; it also represents a simple way of measuring the dispersion and spatial intensity-profile of the cavity modes. The optimization of the cavity performance via the strong Raman process is extremely helpful in achieving efficient cavity-outcoupling of the relatively weak emission of single color-centers such as nitrogen-vacancy centers in diamond or rare-earth ions in crystalline hosts with low emitter density.

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Section: Resultsmentioning

confidence: 99%

Cavity-Enhanced Raman Scattering for In Situ Alignment and Characterization of Solid-State Microcavities

et al. 2020

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“…At the same time, it is necessary to maintain scalability of such devices which is an advantage inherent to solid state emitters. Among potential candidates [1,2], colour centres in diamond were shown to be highly suitable to encounter many of the tasks set in QIP such as coherent manipulation of single spins with long coherence times [3][4][5][6], single photon nonlinearities [7], strong light-matter interactions [8] and entanglement of remote spins [9,10]. More specifically, two colour centres raised strong interest, i.e.…”

Section: Introductionmentioning

confidence: 99%

Spectroscopic investigations of negatively charged tin-vacancy centres in diamond

et al. 2020

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The recently discovered negatively charged tin-vacancy centre in diamond is a promising candidate for applications in quantum information processing (QIP). We here present a detailed spectroscopic study encompassing single photon emission and polarisation properties, the temperature dependence of emission spectra as well as a detailed analysis of the phonon sideband and Debye-Waller factor. Using photoluminescence excitation spectroscopy we probe an energetically higher lying excited state and prove fully lifetime limited linewidths of single emitters at cryogenic temperatures. For these emitters we also investigate the stability of the charge state under resonant excitation. These results provide a detailed insight into the spectroscopic properties of the SnV − centre and lay the foundation for further studies regarding its suitability in QIP.

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“…Nonetheless, the operations that the parties are required to perform seem to be within technological reach [49,50]. In particular, the qubit system could be realized by a nitrogen-vacancy electron spin, whose coherence time has recently reached the order of seconds [51]. The entanglement between the electron spin and the photon's Fock state would then be generated via selective optical pulses and coherent rotations [49], which would entangle the electron spin with the presence or absence of a photon.…”

Section: Multipartite Qkd With a W Statementioning

confidence: 99%

Conference key agreement with single-photon interference

2019

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The intense research activity on Twin-Field (TF) quantum key distribution (QKD) is motivated by the fact that two users can establish a secret key by relying on single-photon interference in an untrusted node. Thanks to this feature, variants of the protocol have been proven to beat the point-to-point private capacity of a lossy quantum channel. Here we generalize the main idea of the TF-QKD protocol introduced by Curty et al to the multipartite scenario, by devising a conference key agreement (CKA) where the users simultaneously distill a secret conference key through single-photon interference. The new CKA is better suited to high-loss scenarios than previous multipartite QKD schemes and it employs for the first time a W-class state as its entanglement resource. We prove the protocol's security in the finite-key regime and under general attacks. We also compare its performance with the iterative use of bipartite QKD protocols and show that our truly multipartite scheme can be advantageous, depending on the loss and on the state preparation.The most mature and developed application of quantum communication [1, 2] is certainly quantum key distribution (QKD) [3][4][5][6][7][8]. The majority of the QKD protocols proposed so far involve just two end-users, Alice and Bob, who want to establish a secret shared key. Nowadays there is a vibrant research towards protocols which are proven to be secure in the most adversarial situation possible (i.e. reducing the assumption on the devices) [9-14], but at the same time are also implementable with today's technology [15][16][17][18]. In this context, a protocol which recently received great attention is the Twin-Field (TF) QKD protocol originally proposed by Lucamarini et al [19], further developed to prove its security [20][21][22][23][24][25][26][27] and experimentally implemented [28][29][30][31]. Indeed, the TF-QKD protocol relies only on single-photon interference occurring in an untrusted node, making it a measurement-device-independent (MDI) QKD protocol capable of overcoming the repeaterless bounds [32,33].In a scenario where several users are required to share a common secret key, one can for instance perform bipartite QKD protocols between pairs of users and then use the secret keys established in this way to encode the final common secret key. Alternatively, one can perform a truly multipartite QKD scheme-also known as conference key agreement (CKA)-whose purpose is to deliver the same secret key to all the parties involved in the protocol [35][36][37][38][39]. In order to accomplish such a task, a resource which seems necessary is the multipartite Greenberger-Horne-Zeilinger (GHZ) state [34][35][36][37][38] or a multipartite private state-a 'twisted' version of the GHZ state [40,41].In this work we introduce a CKA which exploits for the first time the multipartite entanglement of a W-class state [42], in order to deliver the same secret key to all users. Despite having a number of users involved, the scheme relies on single-photon interference in an untrusted no...

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One-second coherence for a single electron spin coupled to a multi-qubit nuclear-spin environment

Cited by 265 publications

References 66 publications

Cavity-Enhanced Raman Scattering for In Situ Alignment and Characterization of Solid-State Microcavities

Cavity-Enhanced Raman Scattering for In Situ Alignment and Characterization of Solid-State Microcavities

Spectroscopic investigations of negatively charged tin-vacancy centres in diamond

Conference key agreement with single-photon interference

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