Yes, there are quantum computers that are accessible to the public online. Several companies and organizations have made efforts to provide cloud-based access to quantum computers, allowing users to run quantum algorithms and experiments remotely.
One notable example is IBM's Quantum Experience, which provides access to their quantum processors through the cloud. Users can write and run quantum programs using IBM's Quantum Composer or Qiskit, a Python-based quantum programming framework. IBM's quantum computers are based on superconducting qubits.
Other companies, such as D-Wave Systems, focus on quantum annealing and provide cloud access to their quantum computers. Quantum annealers are designed for solving optimization problems.
Additionally, various startups and research institutions have made their quantum computers accessible through cloud platforms, allowing users to experiment with quantum algorithms and gain hands-on experience.
It's worth noting that the available quantum computers through these cloud platforms are currently in the early stages of development, and the number of qubits and their coherence times might be limited compared to more advanced, private research facilities. Nonetheless, cloud-based quantum computing platforms provide an opportunity for researchers, developers, and enthusiasts to explore and learn about quantum computing without the need for specialized hardware or infrastructure.
If you're interested in exploring quantum computing, I recommend checking out the cloud platforms provided by IBM, D-Wave Systems, or other quantum computing companies to gain hands-on experience and learn about quantum programming and algorithms.