Quantum Computing

Quantum Computing

Quantum computing requires lasers with very narrow spectral linewidth. Modulight offers the required extreme level of accuracy, control, and innovation for delivering the solutions for tomorrow’s quantum computers – starting from a single laser to complex and powerful solutions based on Modulight's decades of knowledge.

Quantum computing

Quantum computing is a rapidly growing field that aims to develop computers that utilize quantum mechanical phenomena to process information. Unlike classical computers, which use binary digits known as bits to represent information as 0s and 1s, quantum computers use qubits, which can exist in a superposition of states and can be entangled with other qubits.

The superposition of states allows qubits to perform multiple computations in parallel, giving quantum computers the potential to solve problems that are intractable for classical computers. For example, quantum computers can be used to factor large numbers, simulate complex quantum systems, analyze molecule structures, and optimize complex processes.

One of the key challenges in quantum computing is to maintain the coherence of the qubits, which are highly sensitive to their environment. Any interaction with the environment can cause decoherence, which can lead to errors in the computation. This requires careful engineering and control of the qubits, as well as the development of error correction techniques.

Another challenge in quantum computing is the scalability of the technology. While small quantum computers with a few qubits have been developed, it is still a long way to go to develop large-scale quantum computers with hundreds or thousands of qubits. Despite the challenges, quantum computing has the potential to revolutionize many areas of science and technology, from materials science and drug discovery to cryptography and finance. As the benefits and promises of quantum technology are so lucrative, quantum technology is collecting increasing amount of investment. As a result, the development of quantum hardware, software, and algorithms is evolving rapidly, with many researchers and companies working to push the boundaries of what is possible.

Creating qubits

Qubits are typically created using physical systems that exhibit quantum behavior, such as superconducting circuits, atom and ion traps, or photonic systems.

One of the most common approaches to creating qubits is to use superconducting circuits, which consist of tiny loops of superconducting wire that are cooled to near absolute zero temperatures. In these circuits, electrical current can flow virtually indefinitely without resistance, allowing the circuit to exist in multiple states simultaneously. These states can be used to represent qubits.

Another approach to creating qubits is to use ion traps, which use electric and magnetic fields to trap ions in a specific location. By manipulating the state of the trapped ions, one can create qubits. Optical systems, which use laser light to manipulate the state of atoms or other particles, are also used to create qubits.

Once qubits are created, they must be carefully controlled and manipulated in order to perform computations. This can be a challenging task, as qubits are notoriously fragile and prone to errors. However, researchers are developing new techniques for error correction and fault tolerance that could make it possible to build larger and more reliable quantum computers in the future.

Creating qubits using trapped ions

In this approach, qubits are created by encoding quantum information in the internal states of charged ions, which are trapped using electric and magnetic fields. To create trapped ion qubits, one first needs to create a cloud of ions, typically by ionizing a sample of atoms using a laser. The ions are then cooled using a combination of laser cooling and other techniques, such as buffer gas cooling or sympathetic cooling with other ions.

Once the ions are cooled, they can be trapped using a combination of electric and magnetic fields. The most common type of trap used for trapped ion qubits is the Paul trap, which uses an oscillating quadrupole field to confine the ions in a small region of space.

The qubits themselves are created by encoding quantum information in the internal states of the trapped ions. This is typically done using two different energy levels of the ions, which can be manipulated using laser pulses. By carefully controlling the timing and frequency of these pulses, stable and reliable qubits can be created.

Trapped ion qubits have many advantages over other types of qubits, including long coherence times, high fidelity, and low error rates. They also allow for easy manipulation and control of individual qubits, making them ideal for quantum computing applications.

Overall, creating qubits using trapped ions is a powerful technique for quantum computing, and has many potential applications in fields ranging from materials science to cryptography.

Creating qubits using neutral atoms

In this approach, qubits are created by encoding quantum information in the internal states of the neutral atoms. Neutral atoms have long coherence times and are relatively immune to environmental noise.

One common technique for creating qubits using neutral atoms is to use an array of optical tweezers to trap and manipulate individual atoms. The tweezers are created by focusing laser beams to a small spot, creating a three-dimensional trap that can be moved around to pick up and manipulate atoms. By using a combination of laser cooling and magneto-optical trapping, one can cool the atoms down to a few hundred microkelvin, which is cold enough to trap the atoms in the tweezers.

Once the atoms are trapped in the tweezers, they can be manipulated to create qubits. One approach is to use the hyperfine states of the atoms, which can be controlled using microwave or radiofrequency pulses. By carefully controlling the timing and frequency of these pulses, qubits that are stable and reliable can be created.

Another approach to creating qubits using neutral atoms is to use Rydberg atoms, which are atoms that have been excited to high-energy states. In these states, the atoms have very large and long-range dipole moments, which can be used to create strong interactions between the atoms. By controlling the interactions between the Rydberg atoms, one can create qubits that are highly entangled and can perform complex computations.

Magneto-optical trap

A magneto-optical trap (MOT) is a device used in physics to cool and trap neutral atoms using a combination of magnetic fields and laser light. This technique is critical for many applications in atomic physics, quantum computing, and precision measurement.

The basic idea behind a magneto-optical trap is to use laser light to slow down atoms and then trap them using magnetic fields. The process begins with a cloud of atoms that are heated and moving randomly. A series of lasers are then used to cool the atoms by slowing down their movement. As the atoms slow down, they become more susceptible to the effects of magnetic fields.

The MOT uses three pairs of coils to create a magnetic field that is “quadrupole” in shape. This means that the field has a minimum in the center and increases in strength as you move away from the center. The laser light is then tuned to a specific frequency that matches the resonant frequency of the atoms. When the laser light is absorbed by the atoms, they are pushed towards the center of the trap, where the magnetic field is the weakest. This causes the atoms to become trapped in the center of the trap.

Once the atoms are trapped in the MOT, they can be further cooled using a process known as evaporative cooling. In this process, the magnetic field is gradually reduced, causing the highest-energy atoms to escape the trap. As a result, the remaining atoms become colder and colder.

Laser cooling

Laser cooling is a technique used to slow down the movement of atoms and other particles, allowing them to be trapped and manipulated with greater precision. This technique is crucial for many applications in physics and engineering, including quantum computing, atomic clocks, and precision measurements.

The basic idea behind laser cooling is to use lasers to exert a force on atoms that slows down their motion. When an atom absorbs a photon of light, it gains momentum in the direction of the photon’s travel. By carefully tuning the frequency and intensity of the laser light, atoms can be manipulated to absorb and emit photons in a way that slows down their overall motion.

One common technique for laser cooling is known as Doppler cooling, which is used to cool atoms that are moving quickly relative to the laser. In Doppler cooling, the frequency of the laser light is tuned slightly below the resonant frequency of the atom. When an atom moving towards the laser absorbs a photon, it is pushed backwards, reducing its velocity. When using multiple lasers in different directions, cooling of atoms in all three dimensions is possible.

Another technique for laser cooling is known as Sisyphus cooling, which is used to cool atoms that are already moving slowly. In this technique, the laser light is tuned to a frequency that is slightly off-resonant with the atoms. When an atom absorbs a photon, it gains a small amount of energy and is pushed to a slightly higher energy level. However, the atom quickly loses this energy due to collisions with other atoms and emits a photon in a random direction. This process repeats many times, effectively trapping the atom and cooling it down.

Laser linewidth is an important parameter in quantum computing because it affects the coherence and stability of qubits, which are the basic building blocks of quantum information processing. In particular, laser linewidth affects the fidelity of operations performed on qubits, as well as the rate of errors and decoherence in the system.

In quantum computing, laser light is used to manipulate and control qubits, typically by applying pulses of laser light with specific frequencies and durations. The frequency of the laser light must be precisely controlled to ensure that it matches the frequency of the qubit transition, which is determined by the energy levels of the qubit. The linewidth of the laser determines how well it matches the exact frequency of the qubit transition.

If the linewidth of the laser is too broad, it may not be possible to precisely match the frequency of the qubit transition, leading to errors in the operations performed on the qubit. In addition, if the linewidth is too broad, it can cause unwanted interactions between the laser light and other qubits in the system, leading to decoherence and errors.

On the other hand, if the linewidth of the laser is too narrow, it may not be possible to effectively manipulate the qubits, as the laser may not be able to interact with the qubits at the required frequency. This can also lead to errors in the operations performed on the qubit.

Therefore, it is important to carefully control the linewidth of the laser to ensure that it matches the exact frequency of the qubit transition and is able to effectively manipulate the qubits without causing unwanted interactions or errors. This requires careful engineering and control of the laser system, as well as precise characterization of the qubit system.

Modulight solutions for Quantum Computing

As explained above, quantum computing requires stabilized low-noise narrow-linewidth lasers. ML6600 platform for quantum applications includes a high stability low-noise driver, high stability temperature controller, and improved isolation against external perturbation.

  • Preventive maintenance with predictive analytics and machine learning algorithms: Analyzes laser diode performance and predicts future failures & ensures high up-time
  • Broad range of wavelengths from UV to 2+ μm, enabled by diode, solid state, and fiber laser technologies.
  • All manufactured in-house at Modulight fab
  • Technology roadmap towards Photonic Integrated Circuits

ML6600: Cloud-powered laser solution platform 

ML6600 is a compact, easy-to-integrate laser solution that can be flexibly tailored to support Quantum Computing and other Quantum technology laser requirements.  ML6600 provides in a compact package support for multiple different wavelengths (UV to 2 μm), low noise electronics, and integrated optics to create the narrow linewidth lasers needed in Quantum applications. In its own laser fab, Modulight can tailor the wavelengths to meet Quantum requirements and can ensure supply chain security for tens of years.

Designing and customizing lasers at Modulight laser fab 

Modulight has unique, vertically integrated laser fab, containing 62,000 sqft of cleanroom and assembly areas. We have a full stack starting from design, epitaxial growth of laser structures, ranging into processing, testing and system assembly. Also the the product software, Modulight Cloud with its analytics and predictive maintenance features are developed inhouse.  Thanks to all this, we are well-equipped to develop novel lasers for our customers.

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