An ambitious proposal suggests that a giant quantum computer able to solve currently computationally unsolvable problems such as factoring large numbers could be built based on existing technology. Winfried Hensiger of the University of Sussex in the UK and colleagues propose a football-field-sized microwave-coupled trapped-ion quantum computer using thousands of hand-sized modules, each containing 2500 trapped-ion qubits, which could be joined to make an arbitrarily large computer. To factor a 2048 bit (617 digit)-long number (a task impossible on classical computers today) would need, including error correction, some two billion qubit ions, and the calculation would take around 110 days. Quantum computing might start to develop along lines similar to experimental high-energy physics with large facilities funded by international collaborations.