Quantum Teleportation Between Quantum Dots: Paving The Way For The Quantum Internet
By John Oncea, Editor
Researchers have achieved quantum teleportation between photons from different quantum dots, marking a key milestone for a solid-state quantum internet and long-distance photonic networks.
Researchers at the University of Stuttgart and their collaborators have made a landmark advance in quantum communication by teleporting the quantum state of a photon between two physically separated and technically distinct semiconductor quantum dots (QDs), a feat that moves the vision of the quantum internet decisively forward.
This unprecedented demonstration, detailed in Nature Communications, overcomes long-standing barriers around making photons from separate sources indistinguishable, one of the most formidable technical hurdles in distributed quantum networks.
What Is Quantum Teleportation?
Quantum teleportation is a process by which a quantum state – such as the polarization of a photon – can be transferred from one location to another without the actual particle making the journey in a classical sense, according to Study Finds.
In a typical photonic protocol, teleportation leverages two ingredients: an entangled quantum channel and a classical communication channel. The sender prepares the state to be teleported and performs a joint measurement (a Bell-state measurement) between this photon and one half of a pair of entangled photons.
Following this measurement and the transmission of its outcome via classical means, the state of the distant photon is transformed to match the original, even as the original is destroyed in the process. This method ensures that no information travels faster than light, in accordance with quantum mechanics and relativity, and respects the no-cloning theorem, which dictates that quantum information cannot be copied.
Teleportation has a unique importance for photonic quantum networks. In such networks, the quantum bits – or qubits – are typically encoded in the polarization or other degrees of freedom of single photons. These photons serve as the carriers of quantum information because they are relatively resilient to decoherence, especially when traveling through optical fiber.
However, unlike classical signals, quantum information cannot simply be amplified or copied. Teleportation provides the solution, allowing the transfer of quantum states while preserving their delicate quantum coherence, an essential building block for quantum repeaters and, ultimately, for a scalable quantum internet.
The Stuttgart Experiment: Engineering Indistinguishability
What makes the Stuttgart team’s achievement groundbreaking is their use of two truly independent quantum-dot emitters, according to the University. Previous demonstrations of teleportation typically relied on a single device or on sources that were engineered to be virtually identical under ideal lab conditions. Here, by contrast, one quantum dot generated a single photon initialized in a specific polarization state, while the other produced pairs of entangled photons. The experimental challenge was formidable: photons emitted from different quantum dots naturally differ slightly in color (frequency) and timing, making them distinguishable and unsuitable for quantum interference, according to Phys.org.
The team solved this by embedding the quantum dots in circular Bragg resonators and using a combination of multi-axial strain, magnetic fields, and piezoelectric actuators to tune their emission characteristics as closely as possible, according to Slashdot. To completely compensate for the remaining differences, they used quantum frequency converters, sophisticated devices that can shift the wavelength of a photon while preserving its quantum state. As a result, photons from both sources became indistinguishable enough to interfere, a necessary condition for performing a Bell-state measurement.
In the experiment, a photon from one quantum dot was prepared in a state to be teleported. This photon, together with one photon from the entangled pair generated by the second quantum dot, met at the Bell-state measurement station. If the measurement succeeded, information about the result was sent via a classical channel, allowing the remote photon (the remaining half of the entangled pair) to assume the original polarized state. The separation between the two quantum dots in this demonstration was about 10 meters using optical fiber, serving as a laboratory-scale model for longer network links.
The Experimental Results: Fidelity, Efficiency, And Significance
The researchers succeeded in teleporting polarization states between photons from two separate quantum dots, something that had not been achieved before due to the technical complexities involved in matching their emission properties. They reported a teleportation fidelity of 72.1%, meaning the probability that the transferred state matched the original exceeded 2/3 (about 66.7%), the classical limit. This result places the demonstration solidly in the realm of genuine quantum teleportation.
Their setup achieved a two-photon interference visibility of about 30% under loose filtering and up to 79% in supplementary tests with tighter temporal control, according to ScienceBlog. Such high visibility is important because it reflects how well the two photons can interfere, the key to successful measurement-based teleportation protocols.
Importantly, the photon states were successfully converted into telecom-compatible wavelengths, indicating that this technology is compatible with existing optical fiber infrastructure and not just limited to exotic laboratory scales.
What This Means Now For Photonics And Quantum Communications
This experiment stands as a proof-of-concept that quantum teleportation is feasible between distinct, solid-state photon sources engineered for network compatibility. For practicing photonics engineers, the implications are immediate and concrete.
The maturing of quantum-dot emitter technology means that heterogeneous, scalable, and manufacturable single-photon sources are achievable with current semiconductor fabrication techniques. Integrating quantum frequency converters enables these sources to operate at telecom wavelengths, fitting seamlessly into today’s fiber-optic networks.
This study also brings quantum repeaters – a critical technology for extending quantum links over long distances – closer to practical realization. Quantum repeaters work by teleporting quantum states from node to node, rather than amplifying a signal classically as in traditional optical communication systems. The demonstration that teleportation fidelity can exceed the classical threshold with separate hardware nodes is evidence that repeaters built from realistic, potentially heterogeneous photonic hardware can become a central part of the quantum network.
The experiment also highlights standardization challenges and future opportunities. With real-world networks likely comprising diverse emitters and detectors, ensuring practical interoperability will require advances in wavelength conversion, timing syncronization, and system integration. The Stuttgart research shows that these challenges are surmountable when combining best-in-class photonic engineering and semiconductor technology.
Where This Will Lead: The Road To Quantum Internet
This research paves the way for a new era in photonic quantum networks. As methodologies for quantum-dot control, frequency conversion, and interference advance, it will become possible to build much longer quantum links, potentially spanning cities and even connecting distant quantum processors. Future experiments will focus on increasing teleportation fidelity (potentially reaching 90% or more), boosting throughput (for higher communication rates), and scaling up system integration to compact, robust photonic modules.
It is also foreseeable that heterogeneous quantum networks – composed of distinct types of emitters, network nodes, and detectors – will emerge. This will open up opportunities for commercial quantum internet components such as integrated single-photon sources, frequency converters, and quantum-compatible detectors, all designed to work seamlessly with one another. Furthermore, teleportation is not only foundational for communication but also for distributed quantum computing and sensor networks, creating intersections with fields like quantum encryption and remote quantum sensing.
The demonstration of teleportation fidelity above the classical threshold, realized in a network-relevant, fiber-based photonic system, marks a critical inflection point. It signals that challenges related to source mismatch and system scale are being addressed, not just in principle but through practical engineering. This experiment charts a clearer path from research labs into the engineered infrastructure that will eventually underpin the quantum internet, guiding photonics and quantum communications professionals to incorporate quantum-dot emitters and advanced photonic engineering in their future system architectures.
In sum, quantum teleportation between photons from different quantum dots is now not just a proof of quantum weirdness, but a tool in the hands of photonics engineers. The path ahead is illuminated – one photon at a time – by advances like this, bridging the worlds of quantum information science and real-world photonic engineering.