Frequently Asked Questions

A QRNG generates true randomness by measuring a quantum physical process that is intrinsically probabilistic. For example, by splitting a beam of photons and measuring which path an individual photon takes, or by measuring the quantum phase noise of a laser. Because quantum mechanics dictates that these outcomes cannot be determined prior to measurement, the resulting data stream provides perfect, non-deterministic entropy that serves as the foundation for true randomness.

Quantum randomness is essential for high-security cryptographic systems because it eliminates the vulnerabilities associated with algorithmic predictability. If an attacker knows the algorithm and the seed of a pseudo-random generator, they can predict the cryptographic keys and compromise the system. Quantum randomness guarantees that the keys are completely unpredictable, providing a mathematically provable foundation for secure communications, data encryption, and robust device authentication.

Arquis develops ultra-high-speed QRNG solutions by harnessing the phase noise of single-frequency lasers. Our architecture is designed for robust, high-bandwidth applications, processing raw quantum entropy through an advanced Toeplitz Strong Extractor implemented directly on FPGA hardware. This approach allows us to deliver continuous, high-quality true random numbers at speeds up to 26 Gbps, making it ideal for data centres, telecommunications networks, and enterprise cybersecurity.

A photon source is a highly specialized optical device engineered to emit light at the quantum level, either as single photons or as pairs of entangled photons. These sources are the fundamental building blocks of quantum photonics and are essential for executing quantum communication protocols, quantum computing operations, and advanced quantum imaging techniques. They must be carefully tuned to provide high brightness, precise wavelengths, and high fidelity.

A weak coherent photon source operates by heavily attenuating a standard laser pulse until, on average, it contains less than one photon per pulse, making it a highly practical and cost-effective solution for protocols like BB84. In contrast, an entangled photon source relies on non-linear optical processes, such as Spontaneous Parametric Down-Conversion (SPDC), to generate pairs of photons that are quantum-mechanically linked (entangled). Entangled sources are significantly more complex but are required for advanced protocols like E91 and device-independent quantum cryptography.

PPKTP (Periodically Poled Potassium Titanyl Phosphate) and BBO (Beta Barium Borate) are non-linear crystals used inside photon sources to generate entangled photon pairs via spontaneous parametric down-conversion. BBO crystals are typically used for Type-1 and Type-2 phase matching, offering a broad tuning range and excellent reliability for foundational quantum experiments. PPKTP crystals utilize quasi-phase matching, which significantly enhances the conversion efficiency, allowing for ultra-high brightness and exceptional entanglement fidelity suitable for advanced, long-distance quantum communication.

In quantum communication, photon sources act as the transmitters of quantum information. They generate the quantum states (qubits) that are encoded with cryptographic key information—often through polarization or phase encoding—and sent across a fibre optic network or a free-space link. The unique properties of these photons ensure that any attempt by a third party to intercept or measure the transmission will irreversibly alter the quantum state, immediately alerting the communicating parties to the presence of an eavesdropper.

Photon coincidence detection is a technique used to identify when two or more photons arrive at separate detectors at almost exactly the same time. This is a critical measurement in quantum optics used to verify that photon pairs were generated from the same entangled source event, rather than from background noise or separate emissions. It forms the basis of Bell inequality tests, quantum state tomography, and the successful operation of entangled quantum communication networks.

Precise timing is the absolute backbone of quantum systems because quantum events occur on incredibly short timescales, often in the picosecond or nanosecond range. In a quantum network, the transmitter (Alice) and the receiver (Bob) must have their clocks perfectly synchronised to accurately identify and correlate the single photons being transmitted over long distances. Without sub-nanosecond precision, the system cannot distinguish between a true quantum signal and random background noise, causing the communication link to fail.

A Precision Time Protocol (PTP) synchronisation system is an advanced network protocol (IEEE 1588) designed to synchronise clocks throughout a computer network with sub-microsecond precision. In the context of quantum technologies, Arquis utilizes hardware-assisted PTP synchronisation implemented on FPGA fabrics, often combined with White Rabbit protocols, to achieve the ultra-precise, deterministic timing required to align remote quantum nodes across large-scale optical networks.

Coincidence and synchronisation systems act as the command and control infrastructure for quantum experiments. Synchronisation systems ensure that all separate components, lasers, and remote nodes are operating on the exact same timebase. Coincidence systems then monitor the outputs of Single Photon Avalanche Diodes (SPADs), cross-referencing the arrival times of photons across multiple channels to filter out noise, verify entanglement, and successfully extract the quantum data from the raw signal.

Quantum Key Distribution (QKD) is a highly secure communication method that uses the principles of quantum mechanics to establish a shared, secret cryptographic key between two parties. By transmitting the key using individual quantum states (such as the polarization of single photons), QKD guarantees that any attempt to intercept or eavesdrop on the key will inevitably disturb the quantum state, alerting the users. This provides an absolute, physics-based guarantee of forward secrecy.

BB84 is the first and most famous QKD protocol, developed by Charles Bennett and Gilles Brassard in 1984. It works by having the sender (Alice) encode bits of a secret key into the polarization states of individual photons using two different, non-orthogonal bases (e.g., rectilinear and diagonal). The receiver (Bob) randomly chooses bases to measure them. After transmission, Alice and Bob openly compare their chosen bases; they discard the results where their bases didn't match and keep the results where they did, forming a perfectly secure shared key.

Fibre-based QKD transmits quantum signals through standard optical fibre cables, making it highly reliable and easy to integrate into existing telecommunications infrastructure, though it is currently limited in distance (typically 100-200 km) due to signal attenuation. Free-space QKD transmits photons through the air or the vacuum of space, often using satellites or line-of-sight telescopes. While free-space systems must contend with atmospheric turbulence and weather, they suffer from less attenuation in a vacuum, making them the primary technology for achieving global, intercontinental quantum networks.

Photon sources and detectors are the critical hardware endpoints of any QKD system. The photon source acts as the transmitter, generating and encoding the fragile quantum states (either as weak coherent pulses or entangled pairs) that carry the key information. On the receiving end, highly sensitive Single Photon Detectors (such as SPADs or SNSPDs) are required to successfully register the arrival of these individual photons without losing the encoded quantum information, allowing the receiver to decode the key.

A Physical Unclonable Function (PUF) is a hardware security feature that leverages the inherent, uncontrollable microscopic variations that occur during semiconductor manufacturing. Because these physical variations are random and unique to every single silicon chip, a PUF generates a unique digital 'fingerprint' for the device. This fingerprint cannot be copied, cloned, or predicted—even by the original manufacturer—providing a robust, hardware-rooted foundation for cybersecurity.

PUFs are used for device authentication through a challenge-response mechanism. When a server wants to authenticate a device in the network, it sends a digital 'challenge'. The device passes this challenge through its unique PUF hardware circuitry, generating a specific 'response' based on its physical fingerprint. Because no other device in the world has the exact same microscopic variations, only the authentic device can produce the correct response, providing quantum-safe device identity without storing vulnerable secret keys in memory.

Cryptographic security relies entirely on the assumption that encryption keys cannot be guessed or predicted by an attacker. Traditional pseudo-random generators use deterministic algorithms that, while complex, can potentially be modeled or predicted with sufficient computing power or a compromised seed. Quantum randomness removes this vulnerability entirely by providing keys derived from fundamental physical uncertainty. This ensures the cryptographic keys are perfectly random, creating a secure foundation that cannot be broken by algorithmic prediction.

In secure quantum communication systems, synchronisation is vital for maintaining the integrity of the data stream and defending against sophisticated attacks. Perfect synchronisation ensures that the receiver only looks for incoming quantum signals during precise, expected time windows. This drastically reduces the impact of background noise and prevents 'blinding attacks', where an eavesdropper attempts to overwhelm or manipulate the detectors by firing bright light outside of the expected time frame.

Quantum technology is a rapidly emerging field of engineering and physics that seeks to harness the unique, counter-intuitive properties of quantum mechanics—such as superposition, entanglement, and quantum tunneling—to develop revolutionary new applications. By controlling nature at the level of individual atoms and photons, quantum technology aims to create systems that can process information, secure communications, and measure physical properties with capabilities that fundamentally surpass the limits of classical physics.

Quantum photonics involves generating, manipulating, and detecting individual photons of light. Its main applications include Quantum Communication (creating unbreakable encryption networks using QKD), Quantum Computing (using photons as qubits to perform complex calculations faster than classical supercomputers), and Quantum Sensing and Metrology (using entangled light to achieve unprecedented precision in imaging, navigation, and biological measurements).

In research, quantum technologies are providing new tools to study fundamental physics, simulate complex chemical reactions, and develop advanced materials. In industry, quantum technology is poised to revolutionize cybersecurity through quantum-safe encryption, optimise complex logistical and financial models via quantum computing, and provide ultra-precise sensors for medical imaging, autonomous navigation, and mineral exploration, transforming sectors from telecommunications to healthcare.

Arquis is focused on developing the critical hardware infrastructure required to make the quantum internet a reality. Our core technologies include high-speed Quantum Random Number Generators (QRNGs) for ultimate entropy, advanced Photon Sources (both Weak Coherent and Entangled) for quantum transmission, ultra-precise Coincidence and Synchronisation systems for network alignment, and hardware-rooted security modules like Physical Unclonable Functions (PUFs) to secure the next generation of quantum networks.