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تسجيل مستخدم جديدQuantum dots as potential sources of strongly entangled photons for quantum networks
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The generation and long-haul transmission of highly entangled photon pairs is a cornerstone of emerging photonic quantum technologies, with key applications such as quantum key distribution and distributed quantum computing. However, a natural limit for the maximum transmission distance is inevitably set by attenuation in the medium. A network of quantum repeaters containing multiple sources of entangled photons would allow to overcome this limit. For this purpose, the requirements on the sources brightness and the photon pairs degree of entanglement and indistinguishability are stringent. Despite the impressive progress made so far, a definitive scalable photon source fulfilling such requirements is still being sought for. Semiconductor quantum dots excel in this context as sub-poissonian sources of polarization entangled photon pairs. In this work we present the state-of-the-art set by GaAs based quantum dots and use them as a benchmark to discuss the challenges to overcome towards the realization of practical quantum networks.
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An ideal source of entangled photon pairs combines the perfect symmetry of an atom with the convenient electrical trigger of light sources based on semiconductor quantum dots. We create a naturally symmetric quantum dot cascade that emits highly enta
ngled photon pairs on demand. Our source consists of strain-free GaAs dots self-assembled on a triangular symmetric (111)A surface. The emitted photons strongly violate Bells inequality and reveal a fidelity to the Bell state as high as 86 (+-2) % without postselection. This result is an important step towards scalable quantum-communication applications with efficient sources.
The development of scalable sources of non-classical light is fundamental to unlock the technological potential of quantum photonicscite{Kimble:Nat2008}. Among the systems under investigation, semiconductor quantum dots are currently emerging as near
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State-of-the-art quantum key distribution systems are based on the BB84 protocol and single photons generated by lasers. These implementations suffer from range limitations and security loopholes, which require expensive adaptation. The use of polari
zation entangled photon pairs substantially alleviates the security threads while allowing for basically arbitrary transmission distances when embedded in quantum repeater schemes. Semiconductor quantum dots are capable of emitting highly entangled photon pairs with ultra-low multi-pair emission probability even at maximum brightness. Here we report on the first implementation of the BBM92 protocol using a quantum dot source with an entanglement fidelity as high as 0.97(1). For a proof of principle, the key generation is performed between two buildings, connected by 350 metre long fiber, resulting in an average key rate of 135 bits/s and a qubit error rate of 0.019 over a time span of 13 hours, without resorting to time- or frequency-filtering techniques. Our work demonstrates the viability of quantum dots as light sources for entanglement-based quantum key distribution and quantum networks. By embedding them in state-of-the-art photonic structures, key generation rates in the Gbit/s range are at reach.
The ultimate goal of quantum information science is to build a global quantum network, which enables quantum resources to be distributed and shared between remote parties. Such quantum network can be realized by all fiber elements, which takes advant
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