Photon antibunching and magnetospectroscopy of a single fluorine donor in ZnSe

Abstract

We report on the optical investigation of single electron spins bound to fluorine donor impurities in ZnSe. Measurements of photon antibunching establish the presence of single, isolated optical emitters, and magnetooptical studies are consistent with the presence of an exciton bound to the spin-impurity complex. The isolation of this single donor-bound exciton complex and its potential homogeneity offer promising prospects for a scalable semiconductor qubit with an optical interface.PACS numbers: 78.55. Et, Schemes for quantum information processing and quantum communications rely on scalable, robust qubits. In particular, there are many proposals that require fast, efficient, and homogenous single-photon sources 1-3 and still others that rely on the interaction between matter qubits and flying photonic qubits 4 . The requisites for both types of schemes can be satisfied with semiconductor electron spins, which serve as single photon sources 5 or long lived quantum memories with an optical interface 6-8 . However, optical schemes, particularly those based on entanglement, also require large numbers of homogenous photon emitters 9-14 . Electron spins in self-assembled QDs, unfortunately, suffer from large inhomogenities due to their natural size distribution.Impurity-bound electrons in direct bandgap semiconductors, however, have relatively little inhomogeneous broadening 15-20 , yet still possess strong optical transitions when binding an additional exciton 18-21 and long ground state coherence times 7 .An electron bound to a single fluorine donor in ZnSe (F:ZnSe) may serve as a physical qubit with many potential advantages over previously researched qubits. F:ZnSe is particularly appealing because of its nuclear structure compared to III-V-based bound-exciton or quantum dot systems. Unlike III-V systems, isotopic purification of the ZnSe-host matrix to a nuclear-spin-0 background is possible, eliminating magnetic noise from nuclear spin diffusion 22,23 . Further, the F-impurity has a nuclear spin of 1/2 with 100% abundance. Electronnuclear spin swapping schemes 24,25 can be used, which, in combination with the spin-0 background of the isotopically purified host matrix, could lead to an extremely long-lived qubit. Additionally, the applicability of standard microfabrication techniques 26,27 to ZnSe makes the F:ZnSe system particularly scalable.The F:ZnSe system has already shown promise as a scalable source of single photons in Ref. 20. However, a) Electronic address: kdegreve@stanford.edu b) Currently at HRL Laboratories, LLC, 3011 Malibu Canyon Rd., Malibu, CA 90265.this work did not demonstrate the potential of the donor system as a future quantum memory. Here, we show both statistics for single photon emission, as well as the presence of a three-level optical Λ-system through magnetospectroscopy experiments. This introduces F:ZnSe as a valid candidate for use as a scalable qubit with an optical interface.~ 23 meV TES I 2 FE-LH FE-HH c) pump D 0 X D 0 1s 2s,2p I 2 2s-TES 21 meV b) Zn 0.92 Mg 0.08 Se Zn 0.92 M...

Semiconductor qubits based on fluorine implanted ZnMgSe/ZnSe quantum-well nanostructures

“…The Voigt geometry data in Fig.4(b) show a fourfold split with linear polarization which is consistent with F-donor bound-exciton emission. From the measured line splits, we infer an electron g-factor of g e = 1.1(±0.2), which is in good agreement with the value of g e = 1.2 previously measured on epitaxially doped F:ZnSe QWs 15 . The heavy holes in the bound-exciton complex are weakly coupled to the magnetic field, leading to an in-plane heavyhole g-factor |3g ⊥ hh | = 0.0(±0.2) for a 10 nm QW and |3g ⊥ hh | = 0.1(±0.2) for a 4 nm QW.…”

“…We have recently demonstrated the quantum interference between indistinguishable single photons generated by the radiative decay processes of excitons bound to isolated fluorine impurities in ZnMgSe/ZnSe quantum-well (QW) nanostructures 21 . Also, the presence of optically controllable electron spins in a bound-state to a donor in ZnSe has been demonstrated by magneto-spectroscopy 15 . These results were obtained from molecular beam epitaxy (MBE) grown ZnMgSe/ZnSe QWs which were delta-doped with fluorine donors during growth (in the following assumed as "expitaxially doped" QWs).…”

“…The electron bound to a single fluorine donor in ZnSe quantum-wells (QWs) can be engineered as a physical qubit within an external magnetic field 15 . Due to the discrete nature of the QWs, the emission wavelength of an exciton bound to a neutral fluorine donor in the QW is well-defined and the line width remains relatively small.…”

Longitudinal spin relaxation of donor-bound electrons in direct band-gap semiconductors

“…Shallow impurities in direct-bandgap materials are promising candidates for quantum applications relying on spin-photon interfaces [5][6][7], as these systems boast high optical homogeneity [8], strong spinphoton coupling, and the potential in II-VI materials [9] to enhance spin coherence times with isotope purification [10,11]. While electron spin relaxation is now relatively well understood in III-V semiconductor quantum dots both theoretically and experimentally [4,[12][13][14][15][16][17], it is still an open question whether the same processes dominate in the similar direct band-gap donor system.…”

“…In this situation, the splitting of the nf states with m and −m is |m| ω c gµB. To estimate T 1 in this case one should replace (gµB) 9 in Eq. (E25) by (gµB) 7 ( ω c ) 2 in agreement with Eq.…”