Molecular Nanomagnets as Qubits with Embedded Quantum-Error Correction

Abstract

We show that molecular nanomagnets have a potential advantage in the crucial rush toward quantum computers. Indeed, the sizable number of accessible low-energy states of these systems can be exploited to define qubits with embedded quantum error correction. We derive the scheme to achieve this crucial objective and the corresponding sequence of microwave/radiofrequency pulses needed for the error correction procedure. The effectiveness of our approach is shown already with a minimal S = 3/2 unit corresponding to an existing molecule, and the scaling to larger spin systems is quantitatively analyzed.

Targeting molecular quantum memory with embedded error correction

“…We have demonstrated the remarkable performance of our platform in (i) processing quantum information, (ii) swapping it back and forth from the processor to the memory and (iii) fighting decoherence by a targeted QEC procedure on the memory, an effect which could be made even larger by using a larger spin memory. 26 These tasks are achieved by exploiting the electronic Cu spin ½ as an ancilla, whose coherence properties do not affect our scheme. The proposed architecture exploits the best characteristics of the different units: on the one hand the fast manipulations of electronic spin processors and chemical flexibility of Cr 7 Ni rings, on the other hand the intrinsic protection and isolation from the environment provided by nuclear spins.…”

“…A sequence | -1/2⟩ + |1/2⟩ r.f. pulses 26 is then used to transform this state to the encoded superposition . We then wait for a memory time…”

“…A further challenge in producing any scalable quantum computing platform is quantum error correction (QEC), [25][26][27] which is needed to perform complex algorithms with high fidelity. 28 Again molecules could offer a significant advantage.…”

A proposal for using molecular spin qudits as quantum simulators of light–matter interactions

“…Examples are given by Grover's, Fourier transform or Quantum Phase Estimation algorithms 10 or by quantum-error correction schemes recently put forward. [11][12][13] Hence, the qudit-route to the physical implementation of quantum computing appears very promising in the current development stage, where the operations are still noisy and full control of complex quantum devices is hard.…”

“…24,25 Moreover, the spin state of these systems can be easily manipulated by microwave or radio-frequency pulses, 11 thus implementing single-and two-qubit gates in permanently coupled [26][27][28] or scalable architectures. [29][30][31][32][33] Recently, it was proposed to exploit the additional levels typical of these systems for implementing quantum error correction within a single object, [11][12][13] in place of the many qubits required by standard block-codes. 34 Here we show how the qudit nature of magnetic molecules could simplify the practical implementation of important quantum simulation algorithms.…”