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4 results for au:Bayerbach_M in:quant-ph
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Fault-tolerant fusion-based photonic quantum computing (FBQC) greatly relies on entangling two-photon measurements, called fusions. These fusions can be realized using linear-optical projective Bell-state measurements (BSMs). These linear-optical BSMs are limited to a success probability of 50%, greatly reducing the performance of FBQC schemes. To improve the performance of FBQC architectures, a boosted BSM scheme taking advantage of ancillary entangled photon pairs and a 4x4 multiport interferometer has been proposed. This scheme allows the success probability to be increased up to 75%. In this work, we experimentally demonstrate this boosted BSM by using two Sagnac photon-pair sources and a fibre-based 4x4 multiport beam splitter. A boosted BSM success probability of $(69.3\pm0.3)\%$ has been achieved, exceeding the 50% limit. Furthermore, based on our BSMs, we calculate photon-loss thresholds for a fusion network using encoded six-ring resource states. We show that with this boosted BSM scheme an individual photon loss probability of 1.4% can be tolerated, while the non-boosted BSM leads to a photon-loss threshold of 0.45%.
Quantum teleportation has proven to be fundamental for many quantum information and communication processes. The core concept can be exploited in many tasks, from the transmission of quantum states, quantum repeaters, to quantum computing. However, for linear-optical systems, the efficiency of teleportation is directly linked to the success probability of the involved Bell-state measurement. In most implementations, this is realized by linear optics with an intrinsically limited success probability of 50%. Here, we demonstrate quantum teleportation surpassing this limit. We achieve an average fidelity of the teleported states of $0.8677\pm0.0024$, leading to an overall acceptance rate of the teleportation of $69.71\pm0.75\%$. We obtain this boosted success probability by generating ancillary photonic states that are interfered with the Bell states. Thus, our work demonstrates the boosting Bell-state measurements in quantum-technology applications and our scheme could directly be applied to e.g. quantum repeaters.
Bell-state projections serve as a fundamental basis for most quantum communication and computing protocols today. However, with current Bell-state measurement schemes based on linear optics, only two of four Bell states can be identified, which means that the maximum success probability of this vital step cannot exceed $50\%$. Here, we experimentally demonstrate a scheme that amends the original measurement with additional modes in the form of ancillary photons, which leads to a more complex measurement pattern, and ultimately a higher success probability of $62.5\%$. Experimentally, we achieve a success probability of $(57.9 \pm 1.4)\%$, a significant improvement over the conventional scheme. With the possibility of extending the protocol to a larger number of ancillary photons, our work paves the way towards more efficient realisations of quantum technologies based on Bell-state measurements.
We study the impact of distinguishability and mixedness -- two fundamental properties of quantum states -- on quantum interference. We show that these can influence the interference of multiple particles in different ways, leading to effects that cannot be observed in the interference of two particles alone. This is demonstrated experimentally by interfering three independent photons in pure and mixed states and observing their different multiphoton interference, despite exhibiting the same two-photon Hong-Ou-Mandel (HOM) interference. Besides its fundamental relevance, our observation has important implications for quantum technologies relying on photon interference.
Braneshop, and
the US National Science Foundation.
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