TY - CHAP
T1 - Optical read-out of single carrier spin in semiconductor quantum dots
AU - Troiani, F.
AU - Wilson-Rae, I.
AU - Tejedor, C.
PY - 2008/7/1
Y1 - 2008/7/1
N2 - The capability of manipulating and reading-out information at the single-spin level represents a key challenge for spintronics and spin-based quantum information [1, 2]. In semiconductor quantum dots, the strategies so far implemented for the single- spin read-out are based on spinto-charge conversion [3, 4]. There, the dot is electrically manipulated in order to obtain a spin-dependent occupation number. The charge state is then measured with high sensitivity thanks to the dot's capacitive coupling to a quantum-point contact. These measurement schemes, however, imply the tunneling-out of the electron (at least in half of the cases), and therefore the destruction of the quantum state of interest. Projective measurements are instead repeatable, and, in the ideal case, the result of repetitions is completely predictable. This makes them also potential tools for the fast initialization of the qubits [5]. The optical manipulation represents an alternative route to spinbased quantum information [6, 7]. Also there, indirect strategies have been implemented for the initialization and read-out of carrier spins. These rely on the optical selection rules that build-up specific correlations between the spin state of the electron-hole pair and the circular polarization of the light emitted (absorbed) with the pair's annihilation (creation) [8, 9]. As in the previous case, however, the conversion from the spin degree of freedom to the auxiliary ones implies the loss of the spin state, and this impedes the measurement's repetition. In order to achieve a reliable single-spin measurement, an order-of-magnitude increase in the photon collection effciency is needed. Most likely, this might not suffice, unless the possibility of repeatedly probing the same quantum state will also be demonstrated. Photon-collection efficiencies can be largely increased if the dot is optically coupled to an optical microcavity, which mediates its optical emission into free space [10]. The additional requirement that the measurement be non-destructive requires suitable devices and manipulation schemes. Hereafter, we illustrate one such proposals, specifically aimed at implementing a quantum non-demolition measurement of single carrier spin in a dot-cavity system.
AB - The capability of manipulating and reading-out information at the single-spin level represents a key challenge for spintronics and spin-based quantum information [1, 2]. In semiconductor quantum dots, the strategies so far implemented for the single- spin read-out are based on spinto-charge conversion [3, 4]. There, the dot is electrically manipulated in order to obtain a spin-dependent occupation number. The charge state is then measured with high sensitivity thanks to the dot's capacitive coupling to a quantum-point contact. These measurement schemes, however, imply the tunneling-out of the electron (at least in half of the cases), and therefore the destruction of the quantum state of interest. Projective measurements are instead repeatable, and, in the ideal case, the result of repetitions is completely predictable. This makes them also potential tools for the fast initialization of the qubits [5]. The optical manipulation represents an alternative route to spinbased quantum information [6, 7]. Also there, indirect strategies have been implemented for the initialization and read-out of carrier spins. These rely on the optical selection rules that build-up specific correlations between the spin state of the electron-hole pair and the circular polarization of the light emitted (absorbed) with the pair's annihilation (creation) [8, 9]. As in the previous case, however, the conversion from the spin degree of freedom to the auxiliary ones implies the loss of the spin state, and this impedes the measurement's repetition. In order to achieve a reliable single-spin measurement, an order-of-magnitude increase in the photon collection effciency is needed. Most likely, this might not suffice, unless the possibility of repeatedly probing the same quantum state will also be demonstrated. Photon-collection efficiencies can be largely increased if the dot is optically coupled to an optical microcavity, which mediates its optical emission into free space [10]. The additional requirement that the measurement be non-destructive requires suitable devices and manipulation schemes. Hereafter, we illustrate one such proposals, specifically aimed at implementing a quantum non-demolition measurement of single carrier spin in a dot-cavity system.
UR - http://www.scopus.com/inward/record.url?scp=84880189464&partnerID=8YFLogxK
U2 - 10.4032/9789814241199
DO - 10.4032/9789814241199
M3 - Chapter
AN - SCOPUS:84880189464
SN - 9789814241052
SP - 167
EP - 177
BT - Semiconductor Quantum Bits
ER -