We present a high-fidelity quantum teleportation experiment over a high-loss free-space channel between two laboratories.We teleported six states of three mutually unbiased bases and obtained an average state fidelity of 0.82(1), well beyond the classical limit of 2/3.With the obtained data, we tomographically reconstructed the process matrices of quantum teleportation.The free-space channel attenuation of 31 dB corresponds to the estimated attenuation regime for a down-link from a low-earth-orbit satellite to a ground station.We also discussed various important technical issues for future experiments, including the dark counts of single-photon detectors, coincidence-window width etc.Our experiment tested the limit of performing quantum teleportation with state-of-the-art resources.It is an important step towards future satellite-based quantum teleportation and paves the way for establishing a worldwide quantum communication network.We present a high-fidelity quantum teleportation experiment over a high-loss free-space channel between two laboratories.We teleported six states of three mutually unbiased bases and obtained an average state fidelity of 0.82(1), well beyond the classical limit of 2/3.With the obtained data, we tomographically reconstructed the process matrices of quantum teleportation.The free-space channel attenuation of 31 dB corresponds to the estimated attenuation regime for a down-link from a low-earth-orbit satellite to a ground station.We also discussed various important technical issues for future experiments, including the dark counts of single-photon detectors, coincidence-window width etc.Our experiment tested the limit of performing quantum teleportation with state-of-the-art resources.It is an important step towards future satellite-based quantum teleportation and paves the way for establishing a worldwide quantum communication network.

Sep 24, 201211 citations

143 km free-space quantum teleportation

Thomas Herbst, Xiao‐Song Ma, Thomas Scheidl +3 more

In the field of quantum communication the teleportation1 of single quanta plays a fundamental role in numerous quantum information-processing protocols. Quantum teleportation allows to faithfully transfer unknown quantum states over arbitrary distances and constitutes a method to circumvent the no-cloning theorem2. Even formally completely independent particles can become entangled via the process of entanglement swapping3. In a future quantum communication network4 this will be of utmost importance, enabling quantum computers to become globally interconnected. In order to prove the feasibility of quantum teleportation under optical link attenuations that will arise in a future space-application scenario, we extended the communication distance to 143 km, employing an optical free-space link between the two Canary Islands of La Palma and Tenerife. This work proofs the feasibility of ground-based freespace quantum teleportation. With our setup we were able to achieve coincidence production rates and fidelities to cope with the optical link attenuation, resulting from various experimental and technical challenges, which will arise in a quantum transmission between a ground-based transmitter and a low-earth-orbiting satellite receiver5. In our experiment we gained an average state fidelity for the teleported quantum states of more than 6 standard deviations beyond the classical limit of 2/3 and a process fidelity of 0.710(42). We expect that many of the features implemented in this experiment will be key blocks for future investigations.In the field of quantum communication the teleportation1 of single quanta plays a fundamental role in numerous quantum information-processing protocols. Quantum teleportation allows to faithfully transfer unknown quantum states over arbitrary distances and constitutes a method to circumvent the no-cloning theorem2. Even formally completely independent particles can become entangled via the process of entanglement swapping3. In a future quantum communication network4 this will be of utmost importance, enabling quantum computers to become globally interconnected. In order to prove the feasibility of quantum teleportation under optical link attenuations that will arise in a future space-application scenario, we extended the communication distance to 143 km, employing an optical free-space link between the two Canary Islands of La Palma and Tenerife. This work proofs the feasibility of ground-based freespace quantum teleportation. With our setup we were able to achieve coincidence production rates and fidelities to cope with the optical link attenuation, resulting from various experimental and technical challenges, which will arise in a quantum transmission between a ground-based transmitter and a low-earth-orbiting satellite receiver5. In our experiment we gained an average state fidelity for the teleported quantum states of more than 6 standard deviations beyond the classical limit of 2/3 and a process fidelity of 0.710(42). We expect that many of the features implemented in this experiment will be key blocks for future investigations.

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIEOct 8, 20141 citation

Teleportation of a Schrödinger's-Cat State via Satellite-Based Quantum Communications

Hung Do, Robert Malaney, Jonathan Green

The Schrödinger's-cat state is created from the macroscopic superposition of coherent states and is well-known to be a useful resource for quantum information processing protocols. In order to extend such protocols to a global scale, we study the continuous variable (CV) teleportation of the cat state via a satellite in low-Earth-orbit. Past studies have shown that the quantum character of the cat state can be preserved after CV teleportation, even when taking into account the detector efficiency. However, the channel transmission loss has not been taken into consideration. Traditionally, optical fibers with fixed attenuation are used as teleportation channels. Our results show that in such a setup, the quantum character of the cat state is lost after 5dB of channel loss. We then investigate the free-space channel between the Earth and a satellite, where the loss is caused by atmospheric turbulence. For a down-link channel of less than 500km and 30dB of loss, we find that the teleported state preserves higher fidelity relative to a fixed attenuation channel. The results in this work will be important for deployments over Earth-Satellite channels of protocols dependent on cat-state qubits.The Schrödinger's-cat state is created from the macroscopic superposition of coherent states and is well-known to be a useful resource for quantum information processing protocols. In order to extend such protocols to a global scale, we study the continuous variable (CV) teleportation of the cat state via a satellite in low-Earth-orbit. Past studies have shown that the quantum character of the cat state can be preserved after CV teleportation, even when taking into account the detector efficiency. However, the channel transmission loss has not been taken into consideration. Traditionally, optical fibers with fixed attenuation are used as teleportation channels. Our results show that in such a setup, the quantum character of the cat state is lost after 5dB of channel loss. We then investigate the free-space channel between the Earth and a satellite, where the loss is caused by atmospheric turbulence. For a down-link channel of less than 500km and 30dB of loss, we find that the teleported state preserves higher fidelity relative to a fixed attenuation channel. The results in this work will be important for deployments over Earth-Satellite channels of protocols dependent on cat-state qubits.

arXiv:1911.04613IEEE Globecom Workshops (GC Wkshps)Dec 1, 20193 citations

Time-Bin and Polarization Superdense Teleportation for Space Applications

Joseph C. Chapman, Trent Graham, Christopher K. Zeitler +2 more

To build a global quantum-communication network, low-transmission, fiber-based communication channels can be supplemented by using a free-space channel between a satellite and a ground station on Earth. We construct a system that generates hyperentangled photonic ``ququarts'' and measures them to execute multiple quantum-communication protocols of interest. We successfully execute and characterize superdense teleportation, a modified remote-state preparation protocol that transfers more quantum information than standard teleportation, for the same classical information cost, and moreover, is in principle deterministic. Our measurements show an average fidelity of $0.94\ifmmode\pm\else\textpm\fi{}0.02$, with a phase resolution of approximately ${7}^{\ensuremath{\circ}}$, allowing reliable transmission of $>{10}^{5}$ distinguishable quantum states. Additionally, we demonstrate the ability to compensate for the Doppler shift, which would otherwise prevent sending time-bin encoded states from a rapidly moving satellite, thus allowing the low-error execution of phase-sensitive protocols during an orbital pass. Finally, we show that the estimated number of received coincidence counts in a realistic implementation is sufficient to enable faithful reconstruction of the received state in a single pass.To build a global quantum-communication network, low-transmission, fiber-based communication channels can be supplemented by using a free-space channel between a satellite and a ground station on Earth. We construct a system that generates hyperentangled photonic ``ququarts'' and measures them to execute multiple quantum-communication protocols of interest. We successfully execute and characterize superdense teleportation, a modified remote-state preparation protocol that transfers more quantum information than standard teleportation, for the same classical information cost, and moreover, is in principle deterministic. Our measurements show an average fidelity of $0.94\ifmmode\pm\else\textpm\fi{}0.02$, with a phase resolution of approximately ${7}^{\ensuremath{\circ}}$, allowing reliable transmission of $>{10}^{5}$ distinguishable quantum states. Additionally, we demonstrate the ability to compensate for the Doppler shift, which would otherwise prevent sending time-bin encoded states from a rapidly moving satellite, thus allowing the low-error execution of phase-sensitive protocols during an orbital pass. Finally, we show that the estimated number of received coincidence counts in a realistic implementation is sufficient to enable faithful reconstruction of the received state in a single pass.

arXiv:1901.07181Physical Review AppliedJul 15, 202048 citations

Experimental simulation of quantum entanglement distribution over a high-loss channel

Juan Yin, Hai-Lin Yong, Wu Yu-Ping +1 more

We experimentally simulate entanglement distribution and demonstrate the violation of Bell’s inequality over 70 dB channel loss. Imaging a communication system which is composed of a satellite-based entangled photon source at a height of 350 km, two satellite-based transmitting telescopes each with a diameter of 13.5 cm, and two receiving telescopes each with a diameter of 100 cm on the ground station. At a minimum ground elevation angle of 10°, the attenuation for optical links to two ground stations over thousand kilometers is comparable to that we have achieved. Furthermore, theoretical and experimental studies demonstrate the key technology researches in entanglement distribution with high loss. First of all, we should reduce the dark noise and raise the time resolution of the system. On this basis, with the brightness enhancement of the source, the system is tolerant of higher link attenuation and long communication distance.We experimentally simulate entanglement distribution and demonstrate the violation of Bell’s inequality over 70 dB channel loss. Imaging a communication system which is composed of a satellite-based entangled photon source at a height of 350 km, two satellite-based transmitting telescopes each with a diameter of 13.5 cm, and two receiving telescopes each with a diameter of 100 cm on the ground station. At a minimum ground elevation angle of 10°, the attenuation for optical links to two ground stations over thousand kilometers is comparable to that we have achieved. Furthermore, theoretical and experimental studies demonstrate the key technology researches in entanglement distribution with high loss. First of all, we should reduce the dark noise and raise the time resolution of the system. On this basis, with the brightness enhancement of the source, the system is tolerant of higher link attenuation and long communication distance.

Acta Physica SinicaJan 1, 20115 citations

Enhanced Uplink Quantum Communication With Satellites via Downlink Channels

Eduardo Villaseñor, Mingjian He, Ziqing Wang +2 more

In developing the global quantum Internet, quantum communication with low-earth-orbit satellites will play a pivotal role. Such communication will need to be two way: effective not only in the satellite-to-ground (downlink) channel but also in the ground-to-satellite channel (uplink). Given that losses on this latter channel are significantly larger relative to the former, techniques that can exploit the superior downlink to enhance quantum communication in the uplink should be explored. In this article, we do just that—exploring how continuous-variable entanglement in the form of two-mode-squeezed vacuum (TMSV) states can be used to significantly enhance the fidelity of ground-to-satellite quantum-state transfer relative to direct uplink-transfer. More specifically, through detailed phase-screen simulations of beam evolution through turbulent atmospheres in both the downlink and uplink channels, we demonstrate how a TMSV teleportation channel, created by the satellite, can be used to dramatically improve the fidelity of uplink coherent-state transfer relative to direct transfer. We then show how this, in turn, leads to the uplink-transmission of a higher alphabet of coherent states. Additionally, we show how non-Gaussian operations, acting on the received component of the TMSV state at the ground station, can lead to further enhancement of the fidelity. Since TMSV states can readily be producedin situon a satellite platform and form a reliable teleportation channel for most quantum states, our work suggests that future satellites forming part of the emerging quantum Internet should be designed with uplink-communication via quantum teleportation in mind.In developing the global quantum Internet, quantum communication with low-earth-orbit satellites will play a pivotal role. Such communication will need to be two way: effective not only in the satellite-to-ground (downlink) channel but also in the ground-to-satellite channel (uplink). Given that losses on this latter channel are significantly larger relative to the former, techniques that can exploit the superior downlink to enhance quantum communication in the uplink should be explored. In this article, we do just that—exploring how continuous-variable entanglement in the form of two-mode-squeezed vacuum (TMSV) states can be used to significantly enhance the fidelity of ground-to-satellite quantum-state transfer relative to direct uplink-transfer. More specifically, through detailed phase-screen simulations of beam evolution through turbulent atmospheres in both the downlink and uplink channels, we demonstrate how a TMSV teleportation channel, created by the satellite, can be used to dramatically improve the fidelity of uplink coherent-state transfer relative to direct transfer. We then show how this, in turn, leads to the uplink-transmission of a higher alphabet of coherent states. Additionally, we show how non-Gaussian operations, acting on the received component of the TMSV state at the ground station, can lead to further enhancement of the fidelity. Since TMSV states can readily be producedin situon a satellite platform and form a reliable teleportation channel for most quantum states, our work suggests that future satellites forming part of the emerging quantum Internet should be designed with uplink-communication via quantum teleportation in mind.

arXiv:2102.01853IEEE Transactions on Quantum EngineeringJan 1, 202132 citations

>{10}^{5}

distinguishable quantum states. Additionally, we demonstrate the ability to compensate for the Doppler shift, which would otherwise prevent sending time-bin encoded states from a rapidly moving satellite, thus allowing the low-error execution of phase-sensitive protocols during an orbital pass. Finally, we show that the estimated number of received coincidence counts in a realistic implementation is sufficient to enable faithful reconstruction of the received state in a single pass.