Beyond the Voltage Battery - Controlling the fundamental quantum properties of matter
Imagine a battery that doesn't provide power in the traditional sense—it doesn't light up bulbs or spin motors. Instead, it powers the next revolution in computing by controlling the fundamental quantum properties of matter. This isn't science fiction; it's the breakthrough reality of the Josephson phase battery, a device that could fundamentally transform quantum computing, medical imaging, and telecommunications.
In 2020, an international team of researchers achieved what was once thought to be nearly impossible: they created the world's first quantum phase battery 3 7 . This remarkable device doesn't push electrons through circuits with voltage but instead shapes the very wave nature of quantum circuits.
Much like a classical battery converts chemical energy into a persistent voltage bias, a phase battery provides a persistent phase bias to the wave function of a quantum circuit 1 5 . This development represents a critical advancement for quantum technologies that rely on phase coherence—a property where the wave patterns of quantum particles remain synchronized.
In the quantum realm, particles don't just exist as discrete points—they behave as waves described by wave functions. These waves have a crucial property called phase, which describes their position in the oscillatory cycle. Think of phase as the timing of a wave's vibration—whether it's at its peak, trough, or somewhere in between.
When two quantum waves are "in phase," their peaks and troughs align perfectly, creating constructive interference. When they're "out of phase," they can cancel each other out.
At the heart of many quantum devices lies the Josephson junction—a quantum structure where two superconductors are separated by a thin nonsuperconducting barrier 4 . Through a remarkable quantum phenomenon called the Josephson effect, superconducting current can tunnel through this barrier without any voltage applied. The amount of current that flows depends critically on the phase difference between the two superconductors.
For decades, scientists have faced a fundamental challenge: the phase rigidity of quantum systems 1 4 . Due to fundamental symmetries in physics (specifically time-reversal and inversion symmetries), the quantum phase in conventional Josephson junctions resists external manipulation. Creating a persistent, controllable phase bias seemed impossible—until the phase battery breakthrough.
The journey to the phase battery began in 2015 when theorists Sebastian Bergeret and Ilya Tokatly proposed a system that could break the phase rigidity of quantum circuits 3 8 . They recognized that by combining materials with specific quantum properties—superconductors, magnetic materials, and strong spin-orbit coupling—they could create a device that would generate a constant phase bias.
Years later, experimentalists Francesco Giazotto and Elia Strambini identified the perfect material combination to bring this theory to life 3 7 . The core of their quantum phase battery consists of:
The researchers conducted a series of meticulous experiments to demonstrate the phase battery functionality:
| Feature | Classical Battery | Quantum Phase Battery |
|---|---|---|
| Energy Source | Chemical reaction | Spin polarization & spin-orbit coupling |
| Output | Persistent voltage bias | Persistent phase bias |
| Circuit Type | Classical electronic | Quantum superconducting |
| Key Application | Powering devices | Phase control in quantum circuits |
| Controlling Field | Not applicable | Magnetic field |
Core "pile" of battery; provides unpaired-spin surface states
Act as poles; enable Josephson junction formation
"Charges" the battery by aligning spins
Essential for converting spin polarization to phase bias
Couples magnetic and superconducting properties
Allows superconducting correlations in nanowire
Phase batteries could revolutionize superconducting qubits—the building blocks of quantum computers 6 . By providing precise phase control, they could help maintain quantum coherence longer and enable more stable quantum operations.
The phase battery can serve as an energy tuner for superconducting flux and hybrid qubits 4 6 .
Superconducting quantum interference devices (SQUIDs) used in medical imaging like magnetoencephalography (which measures brain activity) could achieve unprecedented sensitivity with phase battery technology 4 .
This could lead to earlier detection of neurological disorders and better understanding of brain function.
The phase battery enables persistent multi-valued phase-shifters for superconducting quantum memories 4 6 . This could lead to the development of entirely new forms of superconducting rectifiers and quantum memory elements.
These elements store information in phase states rather than as electrical charges.
The Josephson phase battery represents a paradigm shift in how we think about and control quantum systems. Just as the invention of the classical battery powered the electronic age, the quantum phase battery may well power the coming quantum technology revolution.