Discord-Enabled Teleportation-Inspired Optical Imaging at a Distance

In quantum teleportation, a pair of entangled photons are prerequisite to serve as the quantum channel for quantum state transfer distantly. Here, we report a new strategy of quantum-teleportation-inspired classical optical imaging, which also works non-locally at a distance; however, only a classically correlated light source is used instead of entanglement. In our experiment, we explore the pseudo-thermal light source to offer the teleportation-like channel and employ the sum-frequency generation to perform the Bell-like state measurement. We successfully demonstrate the teleportation-inspired optical imaging of simple characters, Taiji diagram, and the superposition of orbital angular momentum modes. Moreover, we experimentally observe that a better coherence of pseudo-thermal light will result in a lower contrast of the formed images, and thus revealing that non-zero quantum discord offered by pseudo-thermal light, regardless of zero entanglement, plays the pivotal role in sustaining the teleportation-like channel for imaging at a distance.

💡 Research Summary

The authors present a novel “teleportation‑inspired” optical imaging scheme that replaces the entangled photon pair traditionally required for quantum teleportation with a classically correlated pseudo‑thermal light source. By dynamically modulating a spatial light modulator (SLM) with Kolmogorov‑type phase screens, they generate pseudo‑thermal light whose transverse coherence width can be tuned, thereby controlling the amount of quantum discord present in the two‑photon state shared between two parties (Alice and Bob).

The pseudo‑thermal beam is split; one part (photon b) travels to Alice, the other (photon c) to Bob. Alice also possesses a coherent laser beam (photon a) that carries the image to be transmitted. Using a potassium titanyl phosphate (KTP) crystal, Alice mixes photons a and b in a sum‑frequency generation (SFG) process. Because orbital angular momentum (OAM) is conserved in SFG, detection of the fundamental Gaussian component of the up‑converted photon projects photons a and b onto a Bell‑like antisymmetric state (|ψ⁻⟩). This nonlinear “Bell‑state measurement” plays the role of the joint measurement in standard teleportation.

The measurement outcome is communicated classically to Bob, who uses the trigger to open his camera and record photon c. The resulting state of photon c is a mixture of a completely mixed background and a pure component that carries the full OAM spectrum of the original image. When the pseudo‑thermal source is highly incoherent (small coherence width), the probability amplitudes p_ℓ become uniform, the discord of the two‑photon state approaches its maximum, and the background noise is minimized. Consequently, Bob reconstructs an image with high contrast‑to‑noise ratio (CNR).

Experimentally the authors demonstrate the protocol with several test objects: superpositions of OAM modes (ℓ = ±1, ±2, ±3) that produce petal‑shaped intensity patterns, a Taiji symbol, and the letters “G” and “TI”. They acquire the remote images by summing 2 000–20 000 frames and report CNR values ranging from 2.6 to 4.2, comparable to conventional thermal‑light ghost imaging.

A key contribution is the systematic study of how quantum discord influences imaging quality. By varying the turbulence phase loaded onto the SLM, they tune the discord from 0.86 to 0.9999 and measure the corresponding CNR for the “TI” pattern. The data follow the theoretical predictions derived from the discord‑dependent expressions for the two‑photon state, confirming that higher discord yields better image fidelity, while lower discord leads to a rapid degradation of contrast.

The scheme differs from standard ghost imaging in that the illumination beam (a) and the detection beam (c) never interact; the correlation is mediated solely by the shared pseudo‑thermal photons and the nonlinear Bell‑like measurement—an “interaction‑free” ghost imaging configuration. Moreover, the use of SFG enables wavelength conversion, opening the possibility of infrared object illumination combined with visible‑range detection, thereby overcoming detector limitations in traditional ghost imaging.

In the discussion the authors suggest extensions such as multi‑party discord swapping (analogous to entanglement swapping) and cross‑wavelength imaging networks. They also note that, although the protocol does not operate at the single‑photon level and thus is not a true quantum teleportation, it faithfully mimics the essential feature of teleportation: non‑local transfer of information without physically sending the information‑carrying photons.

Overall, the paper demonstrates that quantum discord—despite the absence of entanglement—can serve as a functional resource for non‑local optical imaging, providing a new perspective on the role of non‑classical correlations in classical‑light ghost imaging and suggesting practical routes toward secure, high‑dimensional, and wavelength‑flexible remote imaging systems.