Artificial coherent states of light by multi-photon interference in a single-photon stream

Abstract

Coherent optical states consist of a quantum superposition of different photon number (Fock) states, but because they do not form an orthogonal basis, no photon number states can be obtained from it by linear optics. Here we demonstrate the reverse, by manipulating a random continuous single-photon stream using quantum interference in an optical Sagnac loop, we create engineered quantum states of light with tunable photon statistics, including approximately coherent states. We demonstrate this experimentally using a true single-photon stream produced by a semiconductor quantum dot in an optical microcavity, and show that we can obtain light with g (2) (0) → 1 in agreement with our theory, which can only be explained by quantum interference of at least 3 photons. The produced artificial light states are, however, much more complex than coherent states, containing quantum entanglement of photons, making them a resource for multi-photon entanglement.

On the importance of antimony for temporal evolution of emission from self-assembled (InGa)(AsSb)/GaAs quantum dots on GaP(001)

“…In the last few decades, nano-structures like selfassembled III-V QDs have been investigated due to their wide range of novel physical properties. Advantages in this respect led to a number of different applications, such as active media in semiconductor lasers [1][2][3], as building blocks for quantum information devices, particularly for quantum repeaters [4][5][6], as efficient single and entangled photon sources [7][8][9][10][11][12][13][14][15], including highlyentangled states for quantum computing [16][17][18][19], or as nanomemories [20][21][22][23][24]. Among III-V QDs, particularly type-I indirect (InGa)(AsSb)/GaAs QDs embedded in a GaP(001) matrix [25,26] have recently attracted attention due to their promising use as storage units for the QD-Flash nanomemory cells [25,26], as potentially effective entangled photon sources [27], owing to their smaller fine-structure splitting (FSS) of the ground state exciton compared to well-known type-I systems such as (InGa)As/GaAs [13,14], and as quantum gates [27][28][29][30].…”