Quantum technology often uses qubits (quantum bits) made up of, for example, individual electrons, photons, or atoms. A group of researchers from the Technical University of Delft has demonstrated the ability to teleport an arbitrary qubit state from a single photon to an optomechanical device, which consists of a mechanical structure made up of billions of atoms. Their groundbreaking research, now published in Nature Photonics, enables real-world applications such as the repeater nodes of the quantum internet, as well as allowing the study of quantum mechanics itself in new ways.
The field of quantum opto-mechanics uses optical means to control mechanical motion in the quantum regime. The first quantum effects in microscale mechanical devices were demonstrated about ten years ago. Since then, efforts have focused on the entangled states between optomechanical devices, as well as the demonstration of an optomechanical quantum memory.
Quantum teleportation - the faithful transfer of an unknown input quantum state to a remote quantum system - is a key component of the long-distance quantum communication protocols necessary to build a quantum internet. Like the normal Internet, the distribution of quantum information between quantum devices anywhere in the world will require a network of repeater nodes.
In their experiment, the researchers create a polarization-encoded photonic qubit in an arbitrary quantum state. They then transport this photon through dozens of meters of fiber optics and teleport it into their quantum memory, made up of two huge silicon mechanical resonators, each about 10 micrometers long and made up of tens of billions of atoms. .
Although quantum teleportation has already been demonstrated in various quantum systems, the use of optomechanical devices is a breakthrough because they can be designed to operate at any optical wavelength, including those of low-loss telecommunications fiber. "This wavelength is the one that gives rise to the least transmission loss, allowing the greatest distance between the repeater nodes," says Gröblacher.
In principle, quantum teleportation can be carried out at arbitrary distances. By teleporting a photonic quantum state through tens of meters of optical fiber to a quantum memory, researchers have demonstrated the requirement for a fully functional optomechanical quantum repeater node.
The current research is a big step towards Gröblacher's vision of a future hybrid quantum Internet. " We are working to achieve a heterogeneous network in which there are several physical systems communicating and performing different functionalities, " he says.
In addition to enabling the construction of new quantum technologies, the ability to teleport an arbitrary state of qubits to massive mechanical oscillators can also be used to test quantum physics itself at a fundamental level. While very small systems tend to behave according to the laws of quantum mechanics, large systems are governed by the classical laws of physics.