5 research outputs found
Genuine Counterfactual Communication with a Nanophotonic Processor
In standard communication information is carried by particles or waves.
Counterintuitively, in counterfactual communication particles and information
can travel in opposite directions. The quantum Zeno effect allows Bob to
transmit a message to Alice by encoding information in particles he never
interacts with. The first suggested protocol not only required thousands of
ideal optical components, but also resulted in a so-called "weak trace" of the
particles having travelled from Bob to Alice, calling the scalability and
counterfactuality of previous proposals and experiments into question. Here we
overcome these challenges, implementing a new protocol in a programmable
nanophotonic processor, based on reconfigurable silicon-on-insulator waveguides
that operate at telecom wavelengths. This, together with our telecom
single-photon source and highly-efficient superconducting nanowire
single-photon detectors, provides a versatile and stable platform for a
high-fidelity implementation of genuinely trace-free counterfactual
communication, allowing us to actively tune the number of steps in the Zeno
measurement, and achieve a bit error probability below 1%, with neither
post-selection nor a weak trace. Our demonstration shows how our programmable
nanophotonic processor could be applied to more complex counterfactual tasks
and quantum information protocols.Comment: 6 pages, 4 figure
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Trace-free counterfactual communication with a nanophotonic processor
Abstract: In standard communication information is carried by particles or waves. Counterintuitively, in counterfactual communication particles and information can travel in opposite directions. The quantum Zeno effect allows Bob to transmit a message to Alice by encoding information in particles he never interacts with. A first remarkable protocol for counterfactual communication relied on thousands of ideal optical operations for high success rate performance. Experimental realizations of that protocol have thus employed post-selection to demonstrate counterfactuality. This post-selection, together with arguments concerning a so-called “weak trace” of the particles traveling from Bob to Alice, have led to a discussion regarding the counterfactual nature of the protocol. Here we circumvent these controversies, implementing a new, and fundamentally different, protocol in a programmable nanophotonic processor, based on reconfigurable silicon-on-insulator waveguides that operate at telecom wavelengths. This, together with our telecom single-photon source and highly efficient superconducting nanowire single-photon detectors, provides a versatile and stable platform for a high-fidelity implementation of counterfactual communication with single photons, allowing us to actively tune the number of steps in the Zeno measurement, and achieve a bit error probability below 1%, without post-selection and with a vanishing weak trace. Our demonstration shows how our programmable nanophotonic processor could be applied to more complex counterfactual tasks and quantum information protocols