Sending quantum signals from Earth to a satellite via uplink, a theoretical feasibility study

Amazing stuff! However, it still not a working real uplink!

"Quantum satellites currently beam entangled particles of light from space down to different ground stations for ultra-secure communications. New research shows it is also possible to send these signals upward, from Earth to a satellite; something once thought unfeasible.

This breakthrough overcomes significant barriers to current quantum satellite communications. Ground station transmitters can access more power, are easier to maintain and could generate far stronger signals, enabling future quantum computer networks using satellite relays. ...

China launched the Micius satellite in 2016, which enabled the first experiments with the transmission of quantum-encrypted information from space. In 2025, the Jinan-1 microsatellite extended this progress with a 12,900 km quantum link between China and South Africa. ...

a “downlink”, said Professor Solntsev. “It’s mostly used for cryptography, where only a few photons (particles of light) are needed to generate a secret key.” ...

“The idea is to fire two single particles of light from separate ground stations to a satellite orbiting 500 km above Earth, travelling at about 20,000 km per hour, so that they meet so perfectly as to undergo quantum interference. Is this even possible?” said Professor Devitt.

“Surprisingly, our modelling showed that an uplink is feasible. We included real-world effects such as background light from the earth and sunlight reflections from the Moon, atmospheric effects and the imperfect alignment of optical systems,” he said. ..."

From the abstract:

"Significant work has been done to develop quantum satellites, which generate entangled pairs in space and distribute them to ground stations separated some distance away.

The reverse “uplink” case, where pairs are generated on the ground and swapped on the satellite using an optical Bell measurement, has not been seriously considered due to a prevailing assumption that it is practically infeasible.

In this paper, we illustrate the feasibility of performing Discrete Variable photonic Bell measurements in space by conducting a detailed numerical analysis to estimate the channel efficiency and attainable pair fidelity for various satellite-station configurations.

Our model accounts for a wide range of physical effects such as atmospheric effects, stray photons, and mode mismatch.

Our findings show promise toward the feasibility of photonic Bell measurements in space, which motivates future research toward large-scale satellite-based uplink entanglement distribution."

Credits: Quantenverschränkung gelingt erstmals im Uplink - einst unmöglich

Scientists reveal it is possible to beam up quantum signals (original news release) "New research shows it is feasible to send quantum signals from Earth to a satellite, paving the way for stronger quantum communication networks."

Quantum entanglement distribution via uplink satellite channels (open access)

(Bottom) A schematic of the proposed uplink setup. ... (Top) The Bell-measurement apparatus inside the satellite.

Australian engineers at CSIRO use quantum machine learning for semiconductor fabrication in world first

Good news!

"Engineers at Australia’s national science agency, CSIRO, have performed a world-first use of quantum machine learning to fabricate semiconductors. The research could reshape the way future microchips are designed. ...

The team was particularly interested in modelling the Ohmic contact resistance of the semiconductor material. This property is a measure of the electrical resistance where the semiconductor comes into contact with a metal and the current flows easily between the materials in both directions.

Modelling Ohmic contact resistance is critical to semiconductor design and fabrication, but it’s also a property which is notoriously difficult to model. ...

The team developed an innovative Quantum Kernel-Aligned Regressor (QKAR) architecture.

Their QKAR setup included a Pauli-Z quantum feature map – a mathematical operator which can translate classical data into quantum states in the form of 5 quantum bits, or qubits.

Once data is mapped to the qubits, a quantum kernel alignment layer is used to perform the machine learning. ..."

From the abstract:

"Modeling complex semiconductor fabrication processes such as Ohmic contact formation remains challenging due to high-dimensional parameter spaces and limited experimental data.

While classical machine learning (CML) approaches have been successful in many domains, their performance degrades in small-sample, nonlinear scenarios.

In this work, quantum machine learning (QML) is investigated as an alternative, exploiting quantum kernels to capture intricate correlations from compact datasets. Using only 159 experimental GaN HEMT samples, a quantum kernel-aligned regressor (QKAR) is developed combining a shallow Pauli-Z feature map with a trainable quantum kernel alignment (QKA) layer.

All models, including seven baseline CML regressors, are evaluated under a unified PCA-based preprocessing pipeline to ensure a fair comparison. QKAR consistently outperforms classical baselines across multiple metrics (MAE, MSE, RMSE), achieving a mean absolute error of 0.338 Ω·mm when validated on experimental data.

Noise robustness and generalization are further assessed through cross-validation and new device fabrication.

These findings suggest that carefully constructed QML models can provide predictive advantages in data-constrained semiconductor modeling, offering a foundation for practical deployment on near-term quantum hardware. While challenges remain for both QML and CML, this study demonstrates QML's potential as a complementary approach in complex process modeling tasks."

Australian engineers at CSIRO use quantum AI for semiconductor fabrication in world first

Quantum Kernel Learning for Small Dataset Modeling in Semiconductor Fabrication: Application to Ohmic Contact

Fig. 7 The process of how to build the QML model.

South Africa and Chinese scientists set record with Quantum Satellite Link

Amazing stuff!

World's longest quantum communications link stretches over 8,000 miles "The world’s longest quantum communications link has been set up between China and South Africa, spanning a record-breaking 12,900 km (8,015 miles). The connection takes advantage of quantum physics for “unbreakable” encryption."

Radar Revolution: Quantum Tech Ends Cloaking Dominance by stealth fighter planes and drones with Molly Gambhir

Amazing stuff! Could be a game changer!

Researchers demonstrate the UK’s first long-distance ultra-secure communication over a quantum network

Good news!

"... the network, which uses standard fibreoptic infrastructure, but relies on a variety of quantum phenomena to enable ultra-secure data transfer.

The network uses two types of quantum key distribution (QKD) schemes: ‘unhackable’ encryption keys hidden inside particles of light; and
distributed entanglement: a phenomenon that causes quantum particles to be intrinsically linked.

The researchers demonstrated the capabilities of the network via a live, quantum-secure video conference link, the transfer of encrypted medical data, and secure remote access to a distributed data centre. The data was successfully transmitted between Bristol and Cambridge – a fibre distance of over 410 kilometres.

This is the first time that a long-distance network, encompassing different quantum-secure technologies such as entanglement distribution, has been successfully demonstrated. ..."

Researchers demonstrate the UK’s first long-distance ultra-secure communication over a quantum network | University of Cambridge "Researchers have successfully demonstrated the UK’s first long-distance ultra-secure transfer of data over a quantum communications network, including the UK’s first long-distance quantum-secured video call."

It appears, the presented paper with the title "A UK Nationwide Heterogeneous Quantum Network" has not yet been published according to Google Scholar (or the title changed or is inaccurate?).

Researchers establish new basis for quantum sensing and communication

Amazing stuff! Over my head too! 😊

"Sensing and communication systems based on quantum-mechanical phenomena can greatly outperform today’s systems, in terms of accuracy and reliability, and are considered a pivotal part of developing next-generation networks. Developing quantum information and decision systems that come close to meeting the theoretical quantum advantages has been a longstanding challenge. Now, a team of researchers ... has developed a framework that could open up new ways of pushing such quantum systems all the way to their fundamental limits.

The key to the team’s new approach is the use of what are known as non-Gaussian quantum states. Most works on quantum sensing and communication systems are based on Gaussian states — namely, states of the electromagnetic field that can be described by Gaussian models. However, many quantum systems based on Gaussian states inevitably suffer from limitations that prevent them from achieving the full quantum advantage. ...

The new work proposes a particular category of non-Gaussian states known as photon-varied Gaussian states (PVGSs), which can be produced with current technologies. The team’s findings show that these PVGSs can indeed enhance the accuracy of quantum sensing, as well as improve the reliability of quantum communications. “We provide a unified characterization of PVGSs,” Conti says, “which facilitates the design of optimal quantum states for sensing and communications.” The unified characterization of quantum states not only simplifies theoretical derivations but also enables practical implementations. “We believe that quantum sensing and communication systems employing PVGSs will become a reality in the near future,” he says. ..."

From the abstract:

"Quantum sensing and communication (QSC) is pivotal for developing next-generation networks with unprecedented performance. Many implementations of existing QSC systems employ Gaussian states as they can be easily realized using current technologies. However, Gaussian states lack non-classical properties necessary to unleash the full potential of QSC.

This motivates the use of non-Gaussian states, which have non-classical properties beneficial for QSC. This paper establishes a theoretical foundation for QSC employing photon-varied Gaussian states (PVGSs). The PVGSs are non-Gaussian states that can be generated from Gaussian states using current technologies.

First, we derive a closed-form expression for the generalized bilinear generating function of ordinary Hermite polynomials and show how it can be used to describe PVGSs.

Then, we characterize PVGSs by deriving their Fock representation and their inner product. We also determine equivalence conditions for Gaussian states obtained from arbitrary permutations of rotation, displacement, and squeezing operators.

Finally, we explore the use of PVGSs for QSC in several case studies."

Researchers establish new basis for quantum sensing and communication | MIT News | Massachusetts Institute of Technology

Quantum Sensing and Communication via Non-Gaussian States (open access)

Fig. 1. Block diagram representing the sequence of operations to obtain mixed PVGSs (dashed dotted box) and pure PVGSs (dashed box), respectively defined in (27) and (29), for ζ,μ,ϕ,t , and k given as input parameters.

Flawed Diamonds Make Perfect Quantum Sensors

Recommendable!

"Quantum sensors take the biggest roadblock for quantum computers—unwanted interference, or noise—and turn it into a strength. Noise wrecks quantum computers because the quantum states they use for computation are affected by the slightest disturbances from the environment. But quantum sensors use those disturbances to detect minuscule changes in magnetic and electric fields. ...

Nitrogen-vacancy (NV) centers are defects in specially grown diamonds where neighboring carbon atoms in the crystal lattice have been replaced by a nitrogen atom and a vacancy—a missing carbon atom. The NV defect allows for precise sensing because the NV exhibits excellent quantum behavior—discrete energy levels, spin, and the ability to absorb and emit individual photons—while protected by the robust diamond host. For example, a tiny change in magnetic field can shift the NV’s energy levels, which induces a measurable change in the rate of photons the NV emits. ..."

Flawed Diamonds Make Perfect Quantum Sensors - IEEE Spectrum Tiny faults could find big applications for chips, art history, and more

Simplified atomic structure of the NV center (Source)

The world is one step closer to secure quantum communication on a global scale

Good news! Pardon, it is not the very latest research (first published July 2023). It appears this research goes beyond quantum communication!

Caveat: I am not an expert on quantum computing etc., but I sense this could be some important research.

"Scientists can now efficiently produce nearly perfect entangled photon pairs from quantum dot sources.

Entangled photons are particles of light that remain connected, even across large distances, and experiments on this topic were recognized by the 2022 Nobel Prize in Physics. Combining entanglement with quantum dots, a technology recognized with the Nobel Prize in Chemistry in 2023, the IQC research team aimed to optimize the process for creating entangled photons, which have a wide variety of applications, including secure communications.

“ The combination of a high degree of entanglement and high efficiency is needed for exciting applications such as quantum key distribution or quantum repeaters, which are envisioned to extend the distance of secure quantum communication to a global scale, or link remote quantum computers,”  ... “Previous experiments only measured either near-perfect entanglement or high efficiency, but we're the first to achieve both requirements with a quantum dot.”

By embedding semiconductor quantum dots into a nanowire, the researchers created a source that creates near-perfect entangled photons 65 times more efficiently than previous work. This new source ... can be excited with lasers to generate entangled pairs on command. The researchers then used high resolution single photon detectors provided by Single Quantum in The Netherlands to boost the degree of entanglement.

“Historically, quantum dot systems were plagued with a problem called fine structure splitting, which causes an entangled state to oscillate over time. This meant that measurements taken with a slow detection system would prevent the entanglement from being measured,” ... “We overcame this by combining our quantum dots with a very fast and precise detection system. We can basically take a time stamp of what the entangled state looks like at each point during the oscillations, and that's where we have the perfect entanglement.” ..."

From the abstract (I understand only 2% of what they are saying here):

"An on-demand source of bright entangled photon pairs is desirable for quantum key distribution (QKD) and quantum repeaters. The leading candidate to generate such pairs is based on spontaneous parametric down-conversion (SPDC) in non-linear crystals. However, its pair extraction efficiency is limited to 0.1% when operating at near-unity fidelity due to multiphoton emission at high brightness. Quantum dots in photonic nanostructures can in principle overcome this limit, but the devices with high entanglement fidelity (99%) have low pair extraction efficiency (0.01%). Here, we show a measured peak entanglement fidelity of 97.5% ± 0.8% and pair extraction efficiency of 0.65% from an InAsP quantum dot in an InP photonic nanowire waveguide. We show that the generated oscillating two-photon Bell state can establish a secure key for peer-to-peer QKD. Using our time-resolved QKD scheme alleviates the need to remove the quantum dot energy splitting of the intermediate exciton states in the biexciton-exciton cascade."

The world is one step closer to secure quantum communication on a global scale

The world is one step closer to secure quantum communication on a global scale (original press release) University of Waterloo researchers combine Nobel prize winning concepts to achieve scientific breakthrough

Oscillating photonic Bell state from a semiconductor quantum dot for quantum key distribution

The entangled photon source, an indium-based quantum dot embedded in a semiconductor nanowire (left), and a visualization of how the entangled photons are efficiently extracted from the nanowire.

India bets big on quantum technology

India does not want to be left behind in the race for quantum technology! They are going to invest heavily in research infrastructure.

"India’s considerable investment in the field places it alongside the United States, Europe and Russia. In December 2018, US President Donald Trump signed a bill to invest US$1.2 billion over five years in a national quantum initiative, and in 2016, Europe pledged US$1.13 billion for quantum technologies. Russia is also spending the equivalent of hundreds of millions of dollars on quantum technologies."

India bets big on quantum technology: Latest budget includes more than a billion dollars in funding for quantum computing, communications and cryptography.




India’s finance minister, Nirmala Sitharaman