Programmable Quantum Processors

- Overview

In 2016, the first quantum computers were able to be programmed from a high level user interface. Quantum processors can draw conclusions about one particle by measuring another. For example, they can determine that if one qubit spins upward, the other will always spin downward, and vice versa. 

A logical quantum processor is a programmable quantum processor that can encode up to 48 logical qubits and perform hundreds of logical gate operations.

A Harvard research team led by Mikhail Lukin recently announced the world's first logical quantum processor. The processor can perform operations on 48 qubits that are logically encoded in a redundant form to provide error correction. 

Logical qubits are better able to perform computations without errors than standard qubits. This makes the new device a potentially important step towards practical quantum computing.

- Logical Qubits 

Logical qubits are groups of physical qubits that work together to perform a computation. They are a crucial component in fault-tolerant quantum computing. 

Logical qubits are used for programming and abstraction and clustering of multiple chips. 

 They are also central to quantum error correction schemes. In these schemes, multiple physical qubits are entangled to encode a single logical qubit. This encoding allows errors in individual physical qubits to be detected and corrected without disturbing the information stored in the logical qubit. 

Logical qubits are error-corrected to maintain their quantum state, making them useful for solving a diverse set of complex problems.

- Programmable Quantum Processors

In the field of quantum computing, the truly useful "information currency" is the so-called logical qubit. Through error-corrected bundles of physical qubits, we can store information for quantum algorithms. 

The creation of logical qubits has been the field's most important yet difficult hurdle to overcome. Scientists generally agree that quantum technology cannot truly take off unless quantum computers can operate reliably on logical qubits.

Here are some programmable quantum processors: 

• IBM Heron: This processor has significantly improved error rates, offering a five-times improvement over the previous best records set by IBM Eagle.
• Phononic quantum processor: This processor has several advantages over previously proposed bosonic networks.

Here are some quantum programming languages: 

• Python: This is an actual quantum programming language.
• Q#: This quantum programming language can be used to write and run quantum programs within Visual Studio and VSCode. Programs developed in the QDK can be run on Microsoft's Azure Quantum, and run on quantum computers from Quantinuum, IonQ, and Pasqal.

- Logical Quantum Processor

The Harvard team has developed the world's first programmable quantum processor capable of executing complex algorithms across 48 logical qubits. This overcomes a major barrier by demonstrating large-scale computation with error correction to achieve fault tolerance. 

In December 2023, a team of researchers led by Mikhail Lukin at Harvard announced the development of the world's first programmable logical quantum processor. The processor can perform operations on 48 qubits, which are logically encoded to provide error correction. 

The processor is a significant milestone in quantum computing and a potential turning point in the field. It is the first demonstration of large-scale algorithm execution on an error-corrected quantum computer. The breakthrough could speed up the development of fault-tolerant quantum computing. 

The team built the computer by separating thousands of rubidium atoms in a vacuum chamber. They then used lasers and magnets to cool the atoms to near absolute zero. They used other lasers to create qubits from 280 of the atoms and then entangle them.

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