Spin relaxation and donor-acceptor recombination ofSe+in 28-silicon

Abstract

Selenium impurities in silicon are deep double donors and their optical and electronic properties have been recently investigated due to their application for infrared detection. However, a singlyionised selenium donor (Se + ) possesses an electron spin which makes it a potential candidate as a silicon-based spin qubit, with significant potential advantages compared to the more commonly studied group V donors. Here we study the electron spin relaxation (T1) and coherence (T2) times of Se + in isotopically purified 28-silicon, and find them to be up to two orders of magnitude longer than shallow group V donors at temperatures above ∼ 15 K. We further study the dynamics of donor-acceptor recombination between selenium and boron, demonstrating that it is possible to control the donor charge state through optical excitation of neutral Se 0 .

Characterization of the Si : Se+ Spin-Photon Interface

“…The data is well fit by 1/T 1 = AT 9 + B, with A = 2.0(3) × 10 −9 s −1 K −9 and a temperature independent contribution with a low temperature limit of T 1 = 4.6(1.5) hours, representing a T 9 Raman process and most likely a residual blackbody-related decay process dominating below 2 K. This T 9 Raman process is in agreement with Ref. [27] taken at 0.35 T, which is fit well by 1/T 1 = CT 9 (C = 1.2 × 10 −8 s −1 K −9 ). The disagreement near 5 K may be due to temperature offsets between these two different experimental setups; alternatively, although the T 9 relaxation process is expected to be independent of magnetic field for electron spins [31], this may not apply when comparing between singlet/triplet spin qubits and nearly pure electron spin qubits.…”

“…Although already quite long, this T 1 time is shorter than the ∼30 minute electron T 1 of 31 P measured at 1.6 K and 0.35 T, as well as significantly shorter than the projected electron T 1 times available to 31 P at 1.6 K in Earth's magnetic field [30]. Six minutes is substantially longer than previously measured 77 Se + electron T 1 times collected at higher temperatures [27], but shorter than the ∼337 hour projected T 1 time following a T 9 dependence fitted from this higher-temperature data and extrapolated to 1.6 K (See Fig 1). Here we elucidate the decay mechanisms affecting the 77 Se + singlet/triplet qubit and determine an experimental regime which gives rise to a 276(90) minute (4.6(1.5) hour) T 1 time.…”

“…[28] with permission, as well as electron spin T1 data taken at 0.35 T (orange) reprinted from Ref. [27] with permission. (Inset) Schematic diagram of optical pumping and readout sequence to measure singlet/triplet T1.…”

“…This remarkable uniformity allowed for the hyperfine splitting and the electron spin g-value of the 1s:A ground state of singly-ionized 77 Se to be directly observed through optical excitation into the first excited state, 1s:T 2 :Γ 7 . Following this, initial electron spin characterization at X-band microwave frequencies on 77 Se + demonstrated promising electron spin qubit coherence and lifetime characteristics [27] similar to that of the shallow donors' ultra-long lived electron spins.…”

Rydberg Entangling Gates in Silicon

“…Donor electron spin qubits in silicon are competitive in most of Di Vincenzo's criteria for a quantum computer implementation: scalability (with the added benefit of CMOS compatibility), high-fidelity initialisation and single qubit readout [1] and extremely long coherence times on the order of seconds for electron or hyperfine spins of 31 P or 77 Se + [2][3][4][5].…”