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Macroscopic rotation of photon polarization induced by a single spin.

Arnold C, Demory J, Loo V, Lemaître A, Sagnes I, Glazov M, Krebs O, Voisin P, Senellart P, Lanco L - Nat Commun (2015)

Bottom Line: Such polarization rotations induced by single spins were recently observed, yet limited to a few 10(-3) degrees due to poor spin-photon coupling.The cavity-enhanced coupling between the incoming photons and the solid-state spin results in a polarization rotation by ± 6° when the spin is optically initialized in the up or down state.These results open the way towards a spin-based quantum network.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Photonique et de Nanostructures, CNRS UPR 20, Route de Nozay, 91460 Marcoussis, France.

ABSTRACT
Entangling a single spin to the polarization of a single incoming photon, generated by an external source, would open new paradigms in quantum optics such as delayed-photon entanglement, deterministic logic gates or fault-tolerant quantum computing. These perspectives rely on the possibility that a single spin induces a macroscopic rotation of a photon polarization. Such polarization rotations induced by single spins were recently observed, yet limited to a few 10(-3) degrees due to poor spin-photon coupling. Here we report the enhancement by three orders of magnitude of the spin-photon interaction, using a cavity quantum electrodynamics device. A single hole spin in a semiconductor quantum dot is deterministically coupled to a micropillar cavity. The cavity-enhanced coupling between the incoming photons and the solid-state spin results in a polarization rotation by ± 6° when the spin is optically initialized in the up or down state. These results open the way towards a spin-based quantum network.

No MeSH data available.


Related in: MedlinePlus

Towards spin-projective measurement with a single detected photon.(a) Principle of projective quantum-non-demolition measurement with a single detected photon, provided the two output polarization states are orthogonal (that is, ‹Ψ⇓/Ψ⇑›=0, with /Ψ⇑› and /Ψ⇓› the polarization states associated to the spin states /⇑› and /⇓>, respectively). In this experiment, a half-wave plate (λ/2) and a quarter wave-plate (λ/4) are used to perform unitary transformations mapping states /Ψ⇑› and /Ψ⇓> into states /H> and /V›. The latter are then distinguished using a polarizing beam-splitter (PBS) and single-photon counters (SPCs). (b) Minimal value of /‹Ψ⇓/Ψ⇑›/ achievable for a given set of device parameters C and κ1 /κ (analytic calculations, see Supplementary Note 3): the ideal configuration ‹Ψ⇓/Ψ⇑›=0 can be obtained for a large range of parameters, represented by the white area. The parameters of the current device are represented by a white circle at κ1/κ=0.4 and C=0.2. (c) Maximal value of the mode reflectivity Rm achievable under the condition that ‹Ψ⇓/Ψ⇑›=0. The white circles indicate two sets of parameters (κ1/κ=0.66, C=0.3) and (κ1/κ=0.9, C=2.5). Increasing mode reflectivities are obtained when the device is further optimized. The hatched region corresponds to parameters for which the orthogonality condition can not be achieved.
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f4: Towards spin-projective measurement with a single detected photon.(a) Principle of projective quantum-non-demolition measurement with a single detected photon, provided the two output polarization states are orthogonal (that is, ‹Ψ⇓/Ψ⇑›=0, with /Ψ⇑› and /Ψ⇓› the polarization states associated to the spin states /⇑› and /⇓>, respectively). In this experiment, a half-wave plate (λ/2) and a quarter wave-plate (λ/4) are used to perform unitary transformations mapping states /Ψ⇑› and /Ψ⇓> into states /H> and /V›. The latter are then distinguished using a polarizing beam-splitter (PBS) and single-photon counters (SPCs). (b) Minimal value of /‹Ψ⇓/Ψ⇑›/ achievable for a given set of device parameters C and κ1 /κ (analytic calculations, see Supplementary Note 3): the ideal configuration ‹Ψ⇓/Ψ⇑›=0 can be obtained for a large range of parameters, represented by the white area. The parameters of the current device are represented by a white circle at κ1/κ=0.4 and C=0.2. (c) Maximal value of the mode reflectivity Rm achievable under the condition that ‹Ψ⇓/Ψ⇑›=0. The white circles indicate two sets of parameters (κ1/κ=0.66, C=0.3) and (κ1/κ=0.9, C=2.5). Increasing mode reflectivities are obtained when the device is further optimized. The hatched region corresponds to parameters for which the orthogonality condition can not be achieved.

Mentions: An important figure of merit for quantum applications is the scalar product ‹Ψ⇓/Ψ⇑› between the two possible output polarization states, /Ψ⇑› and /Ψ⇓›, associated to the spin states /⇑› and /⇓›. This scalar product governs the level of measurement quantum back-action induced by the detection of a single-photon on the single spin state, that is, how strongly a single-photon detection event can project the spin in either the /⇑› or /⇓› state. The ideal case ‹Ψ⇓/Ψ⇑›=0 allows a maximal quantum back-action to be obtained, with a single-photon detection event leading to complete spin projection. Indeed, as sketched in Fig. 4a, if /Ψ⇑› and /Ψ⇓› are orthogonal they can be mapped into horizontal (/H›) and vertical (/V›) polarization states, which can then be unambiguously distinguished using single-photon detectors. In such an experiment, a single click on one single-photon counter will project the spin in state /⇑›, while a single click on the other one will project the spin in state /⇓›; this would constitute a projective quantum measurement performed with a single detected photon.


Macroscopic rotation of photon polarization induced by a single spin.

Arnold C, Demory J, Loo V, Lemaître A, Sagnes I, Glazov M, Krebs O, Voisin P, Senellart P, Lanco L - Nat Commun (2015)

Towards spin-projective measurement with a single detected photon.(a) Principle of projective quantum-non-demolition measurement with a single detected photon, provided the two output polarization states are orthogonal (that is, ‹Ψ⇓/Ψ⇑›=0, with /Ψ⇑› and /Ψ⇓› the polarization states associated to the spin states /⇑› and /⇓>, respectively). In this experiment, a half-wave plate (λ/2) and a quarter wave-plate (λ/4) are used to perform unitary transformations mapping states /Ψ⇑› and /Ψ⇓> into states /H> and /V›. The latter are then distinguished using a polarizing beam-splitter (PBS) and single-photon counters (SPCs). (b) Minimal value of /‹Ψ⇓/Ψ⇑›/ achievable for a given set of device parameters C and κ1 /κ (analytic calculations, see Supplementary Note 3): the ideal configuration ‹Ψ⇓/Ψ⇑›=0 can be obtained for a large range of parameters, represented by the white area. The parameters of the current device are represented by a white circle at κ1/κ=0.4 and C=0.2. (c) Maximal value of the mode reflectivity Rm achievable under the condition that ‹Ψ⇓/Ψ⇑›=0. The white circles indicate two sets of parameters (κ1/κ=0.66, C=0.3) and (κ1/κ=0.9, C=2.5). Increasing mode reflectivities are obtained when the device is further optimized. The hatched region corresponds to parameters for which the orthogonality condition can not be achieved.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4339913&req=5

f4: Towards spin-projective measurement with a single detected photon.(a) Principle of projective quantum-non-demolition measurement with a single detected photon, provided the two output polarization states are orthogonal (that is, ‹Ψ⇓/Ψ⇑›=0, with /Ψ⇑› and /Ψ⇓› the polarization states associated to the spin states /⇑› and /⇓>, respectively). In this experiment, a half-wave plate (λ/2) and a quarter wave-plate (λ/4) are used to perform unitary transformations mapping states /Ψ⇑› and /Ψ⇓> into states /H> and /V›. The latter are then distinguished using a polarizing beam-splitter (PBS) and single-photon counters (SPCs). (b) Minimal value of /‹Ψ⇓/Ψ⇑›/ achievable for a given set of device parameters C and κ1 /κ (analytic calculations, see Supplementary Note 3): the ideal configuration ‹Ψ⇓/Ψ⇑›=0 can be obtained for a large range of parameters, represented by the white area. The parameters of the current device are represented by a white circle at κ1/κ=0.4 and C=0.2. (c) Maximal value of the mode reflectivity Rm achievable under the condition that ‹Ψ⇓/Ψ⇑›=0. The white circles indicate two sets of parameters (κ1/κ=0.66, C=0.3) and (κ1/κ=0.9, C=2.5). Increasing mode reflectivities are obtained when the device is further optimized. The hatched region corresponds to parameters for which the orthogonality condition can not be achieved.
Mentions: An important figure of merit for quantum applications is the scalar product ‹Ψ⇓/Ψ⇑› between the two possible output polarization states, /Ψ⇑› and /Ψ⇓›, associated to the spin states /⇑› and /⇓›. This scalar product governs the level of measurement quantum back-action induced by the detection of a single-photon on the single spin state, that is, how strongly a single-photon detection event can project the spin in either the /⇑› or /⇓› state. The ideal case ‹Ψ⇓/Ψ⇑›=0 allows a maximal quantum back-action to be obtained, with a single-photon detection event leading to complete spin projection. Indeed, as sketched in Fig. 4a, if /Ψ⇑› and /Ψ⇓› are orthogonal they can be mapped into horizontal (/H›) and vertical (/V›) polarization states, which can then be unambiguously distinguished using single-photon detectors. In such an experiment, a single click on one single-photon counter will project the spin in state /⇑›, while a single click on the other one will project the spin in state /⇓›; this would constitute a projective quantum measurement performed with a single detected photon.

Bottom Line: Such polarization rotations induced by single spins were recently observed, yet limited to a few 10(-3) degrees due to poor spin-photon coupling.The cavity-enhanced coupling between the incoming photons and the solid-state spin results in a polarization rotation by ± 6° when the spin is optically initialized in the up or down state.These results open the way towards a spin-based quantum network.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire de Photonique et de Nanostructures, CNRS UPR 20, Route de Nozay, 91460 Marcoussis, France.

ABSTRACT
Entangling a single spin to the polarization of a single incoming photon, generated by an external source, would open new paradigms in quantum optics such as delayed-photon entanglement, deterministic logic gates or fault-tolerant quantum computing. These perspectives rely on the possibility that a single spin induces a macroscopic rotation of a photon polarization. Such polarization rotations induced by single spins were recently observed, yet limited to a few 10(-3) degrees due to poor spin-photon coupling. Here we report the enhancement by three orders of magnitude of the spin-photon interaction, using a cavity quantum electrodynamics device. A single hole spin in a semiconductor quantum dot is deterministically coupled to a micropillar cavity. The cavity-enhanced coupling between the incoming photons and the solid-state spin results in a polarization rotation by ± 6° when the spin is optically initialized in the up or down state. These results open the way towards a spin-based quantum network.

No MeSH data available.


Related in: MedlinePlus