Source-linked AI summary
Quantum computing with collective ensembles of multi-level systems
E. Brion, K. Moelmer, M. Saffman
TL;DR
Mediating two-bit gates across many particles remains challenging. The paper encodes bits in collective populations of multilevel ensembles and proposes a trapped-atom implementation that may support 14 qubits.
Problem
Mediating two-bit gates between arbitrary qubit pairs by controlling many particles with suitable interactions remains an outstanding challenge.
Source: p. 1Method
The proposal encodes an N-bit register in symmetric ensemble states, using N+1 internal levels and binary populations in the register states.
Source: pp. 1, 4Results
50–100 cold trapped cesium atoms may allow 14-qubit computing, which the authors say would exceed any proposal implemented to date.
Source: p. 3Takeaways & Limitations
Because register size grows linearly with single-particle internal-state dimension, atoms or molecules with more stable states could conceivably approach 100 bits.
Source: pp. 3–4Coupling strengths vary with register-state populations, though N ≪ K can reduce variation; reliable transition control, efficient gates, and error correction remain challenges.
Source: pp. 2, 4
Abstract
from arXiv · showhide
We propose a new physical approach for encoding and processing of quantum information in ensembles of multi-level quantum systems, where the different bits are not carried by individual particles but associated with the collective population of different internal levels. One- and two-bit gates are implemented by collective internal state transitions taking place in the presence of an excitation blockade mechanism which restricts the population of each internal state to the values zero and unity. 10-20 bit quantum computers can be built via this scheme in single trapped clouds of ground state atoms subject to the Rydberg excitation blockade mechanism, and the linear dependence between register size and the number of internal quantum states in atoms offers realistic means to reach larger registers.