Both photonic quantum computation and the establishment of a quantum internet require fiber-based measurement and feed-forward in order to be compatible with existing infrastructure. Here we present an all-fiber scheme for measurement and feed-forward, whose performance is benchmarked by carrying out remote preparation of single-photon polarization states at telecom-wavelengths. The result of a projective measurement on one photon deterministically controls the path a second photon takes with ultrafast optical switches. By placing well-calibrated passive polarization optics in the paths, we achieve a measurement and feed-forward fidelity of (99.0 $\pm$ 0.5)%. Our methods are useful for photonic quantum experiments including computing, communication, and teleportation.Both photonic quantum computation and the establishment of a quantum internet require fiber-based measurement and feed-forward in order to be compatible with existing infrastructure. Here we present an all-fiber scheme for measurement and feed-forward, whose performance is benchmarked by carrying out remote preparation of single-photon polarization states at telecom-wavelengths. The result of a projective measurement on one photon deterministically controls the path a second photon takes with ultrafast optical switches. By placing well-calibrated passive polarization optics in the paths, we achieve a measurement and feed-forward fidelity of (99.0$\pm$ 0.5)%. Our methods are useful for photonic quantum experiments including computing, communication, and teleportation.

Sep 16, 20200 citations

Quantum teleportation with independent sources over an optical fibre network

Qi-Chao Sun, Ya-Li Mao, Sijing Chen +15 more

Quantum teleportation faithfully transfers a quantum state between distant nodes in a network, enabling revolutionary information processing applications. Here we report teleporting quantum states over a 30 km optical fiber network with the input single photon state and the EPR state prepared independently. By buffering photons in 10 km coiled optical fiber, we perform Bell state measurement after entanglement distribution. With active feed-forward operation, the average quantum state fidelity and quantum process fidelity are measured to be 0.85 and 0.77, exceeding classical limits of 0.67 and 0.5, respectively. The statistical hypothesis test shows that the probability of a classical process to predict an average state fidelity no less than the one observed in our experiment is less than 2.4E-14, confirming the quantum nature of our quantum teleportation experiment. Our experiment marks a critical step towards the realization of quantum internet in the future.Quantum teleportation faithfully transfers a quantum state between distant nodes in a network, enabling revolutionary information processing applications. Here we report teleporting quantum states over a 30 km optical fiber network with the input single photon state and the EPR state prepared independently. By buffering photons in 10 km coiled optical fiber, we perform Bell state measurement after entanglement distribution. With active feed-forward operation, the average quantum state fidelity and quantum process fidelity are measured to be 0.85 and 0.77, exceeding classical limits of 0.67 and 0.5, respectively. The statistical hypothesis test shows that the probability of a classical process to predict an average state fidelity no less than the one observed in our experiment is less than 2.4E-14, confirming the quantum nature of our quantum teleportation experiment. Our experiment marks a critical step towards the realization of quantum internet in the future.

arXiv:1602.07081Feb 23, 20165 citations

Demonstration of feed-forward control for linear optics quantum computation

T. B. Pittman, B. C. Jacobs, J. D. Franson

One of the main requirements in linear optics quantum computing is the ability to perform single-qubit operations that are controlled by classical information fed forward from the output of single-photon detectors. These operations correspond to predetermined combinations of phase corrections and bit flips that are applied to the postselected output modes of nondeterministic quantum logic devices. Corrections of this kind are required in order to obtain the correct logical output for certain detection events, and their use can increase the overall success probability of the devices. In this paper, we report on the experimental demonstration of the use of this type of feed-forward system to increase the probability of success of a simple nondeterministic quantum logic operation from approximately $\frac{1}{4}$ to $\frac{1}{2}.$ This logic operation involves the use of one target qubit and one ancilla qubit which, in this experiment, are derived from a parametric down-conversion photon pair. Classical information describing the detection of the ancilla photon is fed forward in real time and used to alter the quantum state of the output photon. A fiber-optic delay line is used to store the output photon until a polarization-dependent phase shift can be applied using a high-speed Pockels cell.One of the main requirements in linear optics quantum computing is the ability to perform single-qubit operations that are controlled by classical information fed forward from the output of single-photon detectors. These operations correspond to predetermined combinations of phase corrections and bit flips that are applied to the postselected output modes of nondeterministic quantum logic devices. Corrections of this kind are required in order to obtain the correct logical output for certain detection events, and their use can increase the overall success probability of the devices. In this paper, we report on the experimental demonstration of the use of this type of feed-forward system to increase the probability of success of a simple nondeterministic quantum logic operation from approximately $\frac{1}{4}$ to $\frac{1}{2}.$ This logic operation involves the use of one target qubit and one ancilla qubit which, in this experiment, are derived from a parametric down-conversion photon pair. Classical information describing the detection of the ancilla photon is fed forward in real time and used to alter the quantum state of the output photon. A fiber-optic delay line is used to store the output photon until a polarization-dependent phase shift can be applied using a high-speed Pockels cell.

arXiv:quant-ph/0204142Physical Review ANov 14, 200264 citations

Experiments with Generalized Quantum Measurements and Entangled Photon Pairs

Devon N. Biggerstaff

This thesis describes a linear-optical device for performing generalized quantum measurements \non quantum bits (qubits) encoded in photon polarization, the implementation \nof said device, and its use in two diff erent but related experiments. The device works by \ncoupling the polarization degree of freedom of a single photon to a `mode' or `path' degree \nof freedom, and performing a projective measurement in this enlarged state space in order \nto implement a tunable four-outcome positive operator-valued measure (POVM) on the \ninitial quantum bit. In both experiments, this POVM is performed on one photon from a \ntwo-photon entangled state created through spontaneous parametric down-conversion. \nIn the fi rst experiment, this entangled state is viewed as a two-qubit photonic cluster \nstate, and the POVM as a means of increasing the computational power of a given resource \nstate in the cluster-state model of quantum computing. This model traditionally \nachieves deterministic outputs to quantum computations via successive projective measurements, \nalong with classical feedforward to choose measurement bases, on qubits in a highly entangled \nresource called a cluster state; we show that `virtual qubits' can be appended to a \ngiven cluster by replacing some projective measurements with POVMs. Our experimental \ndemonstration fully realizes an arbitrary three-qubit cluster computation by implementing \nthe POVM, as well as fast active feed-forward, on our two-qubit photonic cluster state. \nOver 206 diff erent computations, the average output delity is 0.9832 +/- 0.0002; furthermore \nthe error contribution from our POVM device and feedforward is only of order 10^-3, less \nthan some recent thresholds for fault-tolerant cluster computing. \nIn the second experiment, the POVM device is used to implement a deterministic \nprotocol for remote state preparation (RSP) of arbitrary photon polarization qubits. RSP \nis the act of preparing a quantum state at a remote location without actually transmitting \nthe state itself. We are able to remotely prepare 178 diff erent pure and mixed qubit \nstates with an average delity of 0.995. Furthermore, we study the the fidelity achievable \nby RSP protocols permitting only classical communication, without shared entanglement, \nand compare the resulting benchmarks for average fidelity against our experimental results. \nOur experimentally-achieved average fi delities surpass the classical thresholds whenever \nclassical communication alone does not trivially allow for perfect RSP.This thesis describes a linear-optical device for performing generalized quantum measurements \non quantum bits (qubits) encoded in photon polarization, the implementation \nof said device, and its use in two diff erent but related experiments. The device works by \ncoupling the polarization degree of freedom of a single photon to a `mode' or `path' degree \nof freedom, and performing a projective measurement in this enlarged state space in order \nto implement a tunable four-outcome positive operator-valued measure (POVM) on the \ninitial quantum bit. In both experiments, this POVM is performed on one photon from a \ntwo-photon entangled state created through spontaneous parametric down-conversion. \nIn the fi rst experiment, this entangled state is viewed as a two-qubit photonic cluster \nstate, and the POVM as a means of increasing the computational power of a given resource \nstate in the cluster-state model of quantum computing. This model traditionally \nachieves deterministic outputs to quantum computations via successive projective measurements, \nalong with classical feedforward to choose measurement bases, on qubits in a highly entangled \nresource called a cluster state; we show that `virtual qubits' can be appended to a \ngiven cluster by replacing some projective measurements with POVMs. Our experimental \ndemonstration fully realizes an arbitrary three-qubit cluster computation by implementing \nthe POVM, as well as fast active feed-forward, on our two-qubit photonic cluster state. \nOver 206 diff erent computations, the average output delity is 0.9832 +/- 0.0002; furthermore \nthe error contribution from our POVM device and feedforward is only of order 10^-3, less \nthan some recent thresholds for fault-tolerant cluster computing. \nIn the second experiment, the POVM device is used to implement a deterministic \nprotocol for remote state preparation (RSP) of arbitrary photon polarization qubits. RSP \nis the act of preparing a quantum state at a remote location without actually transmitting \nthe state itself. We are able to remotely prepare 178 diff erent pure and mixed qubit \nstates with an average delity of 0.995. Furthermore, we study the the fidelity achievable \nby RSP protocols permitting only classical communication, without shared entanglement, \nand compare the resulting benchmarks for average fidelity against our experimental results. \nOur experimentally-achieved average fi delities surpass the classical thresholds whenever \nclassical communication alone does not trivially allow for perfect RSP.

Nov 2, 20092 citations

Ultrafast switching of telecom photon-number states

Kate L. Fenwick, Frédéric Bouchard, Alicia Sit +7 more

A crucial component of photonic quantum information processing platforms is the ability to modulate, route, convert, and switch quantum states of light noiselessly with low insertion loss. For instance, a high-speed, low-loss optical switch is crucial for scaling quantum photonic systems that rely on measurement-based feed-forward approaches. Such a device will also ideally be capable of operating on photon-number states, which can act as non-Gaussian resources. Here, we demonstrate ultrafast all-optical switching of heralded photon-number states, of up to 6 photons, using the optical Kerr effect in a single-mode fiber. A local birefringence is created by a high-intensity pump pulse at a center wavelength of 1030 nm which overlaps temporally with the 1550 nm photons in the fiber. A switching efficiency of $>$99 % is reached with a resolution of 2.3 ps, an insertion loss of $2.27\pm0.08$ dB, and a signal-to-noise ratio of 32,000.A crucial component of photonic quantum information processing platforms is the ability to modulate, route, convert, and switch quantum states of light noiselessly with low insertion loss. For instance, a high-speed, low-loss optical switch is crucial for scaling quantum photonic systems that rely on measurement-based feed-forward approaches. Such a device will also ideally be capable of operating on photon-number states, which can act as non-Gaussian resources. Here, we demonstrate ultrafast all-optical switching of heralded photon-number states, of up to 6 photons, using the optical Kerr effect in a single-mode fiber. A local birefringence is created by a high-intensity pump pulse at a center wavelength of 1030 nm which overlaps temporally with the 1550 nm photons in the fiber. A switching efficiency of $>$99 % is reached with a resolution of 2.3 ps, an insertion loss of $2.27\pm0.08$ dB, and a signal-to-noise ratio of 32,000.

arXiv:2504.12376Physical Review AJan 23, 20260 citations

Telecom-wavelength quantum teleportation using frequency-converted photons from remote quantum dots

Tim Strobel, Michal Vyvlečka, Ilenia Neureuther +13 more

A global quantum internet is based on scalable networks, which require reliable quantum hardware. Among them are quantum light sources providing deterministic, high-brightness, high-fidelity entangled photons and quantum memories with coherence times exceeding the millisecond range. Long-distance operation demands quantum light sources emitting at telecommunication wavelengths. A cornerstone for such networks is the demonstration of quantum teleportation. Here, we realize full-photonic quantum teleportation employing semiconductor quantum dots, which can fulfill all the aforementioned requirements. Two remote GaAs quantum dots, emitting in the near-infrared, are used: one as an entangled-photon pair source and the other as a single-photon source. During the experiment, the single photon is prepared in conjugate polarization states and interfaced with the biexciton emission of the entangled pair employing a polarization-selective Bell state measurement. This process teleports the respective polarization state onto the exciton emission of the entangled pair. The frequency mismatch between the triggered sources is erased using two polarization-preserving quantum frequency converters, enabling remote two-photon interference at telecommunication wavelengths, yielding a visibility of 30(1)%. A post-selected teleportation fidelity up to 0.721(33), significantly above the classical limit, demonstrates successful quantum teleportation between light from distinct sources. These results mark an important development for semiconductor-based quantum light sources.A global quantum internet is based on scalable networks, which require reliable quantum hardware. Among them are quantum light sources providing deterministic, high-brightness, high-fidelity entangled photons and quantum memories with coherence times exceeding the millisecond range. Long-distance operation demands quantum light sources emitting at telecommunication wavelengths. A cornerstone for such networks is the demonstration of quantum teleportation. Here, we realize full-photonic quantum teleportation employing semiconductor quantum dots, which can fulfill all the aforementioned requirements. Two remote GaAs quantum dots, emitting in the near-infrared, are used: one as an entangled-photon pair source and the other as a single-photon source. During the experiment, the single photon is prepared in conjugate polarization states and interfaced with the biexciton emission of the entangled pair employing a polarization-selective Bell state measurement. This process teleports the respective polarization state onto the exciton emission of the entangled pair. The frequency mismatch between the triggered sources is erased using two polarization-preserving quantum frequency converters, enabling remote two-photon interference at telecommunication wavelengths, yielding a visibility of 30(1)%. A post-selected teleportation fidelity up to 0.721(33), significantly above the classical limit, demonstrates successful quantum teleportation between light from distinct sources. These results mark an important development for semiconductor-based quantum light sources.

Nature CommunicationsNov 17, 202512 citations

\pm

0.5)%. Our methods are useful for photonic quantum experiments including computing, communication, and teleportation.

\frac{1}{4}

\frac{1}{2}.

This logic operation involves the use of one target qubit and one ancilla qubit which, in this experiment, are derived from a parametric down-conversion photon pair. Classical information describing the detection of the ancilla photon is fed forward in real time and used to alter the quantum state of the output photon. A fiber-optic delay line is used to store the output photon until a polarization-dependent phase shift can be applied using a high-speed Pockels cell.

2.27\pm0.08

dB, and a signal-to-noise ratio of 32,000.