Electron–phonon processes of the silicon-vacancy centre in diamond

Abstract

We investigate phonon induced electronic dynamics in the ground and excited states of the negatively charged silicon-vacancy ( − SiV ) centre in diamond. Optical transition line widths, transition wavelength and excited state lifetimes are measured for the temperature range 4 K-350 K. The ground state orbital relaxation rates are measured using time-resolved fluorescence techniques. A microscopic model of the thermal broadening in the excited and ground states of the − SiV centre is developed. A vibronic process involving single-phonon transitions is found to determine orbital relaxation rates for both the ground and the excited states at cryogenic temperatures. We discuss the implications of our findings for coherence of qubits in the ground states and propose methods to extend coherence times of − SiV qubits. IntroductionColour centres in diamond have emerged as attractive systems for applications in quantum metrology, quantum communication, and quantum information processing [1][2][3]. Diamond has a large band gap which allows for optical control, and it can be synthesized with high purity, enabling long coherence times as was demonstrated for nitrogen-vacancy ( − NV ) spin qubits [4]. Among many colour centres in diamond [5,6], the negatively charged silicon-vacancy ( − SiV ) centre stands out due to its desirable optical properties. In particular, near transform-limited photons can be created with high efficiency due to the strong zero-phonon line emission that constitutes ∼70% of the total emission. − SiV centres can also be created with a narrow inhomogeneous distribution that is comparable to the transform limited optical line width [7]. These optical properties, due to the inversion symmetry of the system which suppresses effects of spectral diffusion, recently enabled demonstration of two-photon interference from separated emitters [8] that is a key requirement for many quantum information processing protocols [9][10][11][12].Interfacing coherent optical transitions with long-lived spin qubits is a key challenge for quantum optics with solid state emitters [13][14][15][16][17]. This challenge may be addressed using optically accessible electronic spins in − SiV centres [18]. It has recently been demonstrated that coherent spin states can be prepared and read out optically [19,20], although the spin coherence time was found to be limited by phonon-induced relaxation in the ground states [19]. Here we present the first systematic study of the electron-phonon interactions that are responsible for relaxation within the ground and excited states of the − SiV centre. This is achieved by measuring the temperature dependence of numerous processes within the centre. A comprehensive microscopic model is then developed to account for the observations. In section 4.1 we discuss the implications of these phonon processes for spin coherences in the − SiV ground state, and identify approaches that could extend the spin coherences.

Cooling phonons with phonons: Acoustic reservoir engineering with silicon-vacancy centers in diamond

“…By using the value g s /2π ≈ 1 PHz, we obtain Γ ph /2π ≈ 1.78 MHz, which is in good agreement with the experimental results found in Ref. [54,55]. The other limiting case, which is more appropriate for the considered transverse beam dimensions of t, w λ ∆ , is the limit of a quasi-1D beam, where the frequencies of all the transverse compression modes exceed ∆.…”

Diamond Spins Shining Bright

“…2(c)]. This is evidence of a single-phonon mechanism for this fast relaxation process [30][31][32], which has significant implications for the spin coherence time discussed below.…”

Coherent control of a strongly driven silicon vacancy optical transition in diamond

“…SiV spin coherence times are in the range of B40 ns at cryogenic (4 K) temperatures 13,14 . It is important to note that the coherence times are only limited by spin relaxation time and are estimated to increase dramatically at lower temperatures 15 . As a result, the SiV defect has become a promising candidate to be a key building block for quantum information processing.…”