Fastest Rubik's Cube Robot: 0.103 Seconds, How Is It Done?

Rubik's Cube robot records over the years

Guinness calls this record "fastest robot to solve a puzzle cube". Here are the milestones, taken from the list Guinness published with its 2025 record news (Guinness World Records):

In just 16 years, the record dropped from over a minute to about a tenth of a second. The one-second barrier fell in 2016, and since then each new record has only been better by hundredths of a second.

For comparison: the WCA world record for a person solving the 3x3 cube is 2.51 seconds for a single solve, set by Xuanyi Geng (WCA). The Purdue robot is about 24 times faster. The story of the 2.51 second record is in the post New 3x3 Rubik's Cube world record: 2.51 seconds.

One thing to keep in mind: robot records are recognised by Guinness, not the WCA. The WCA only runs competitions for people. The two kinds of record have different rules, so you can't compare them directly.

Who is behind the record-breaking robots?

Purdubik's Cube (2025). The team is Matthew Patrohay, Junpei Ota, Aden Hurd and Alex Berta, electrical and computer engineering students at Purdue University, with their supervisor Nak-seung Patrick Hyun. According to Guinness, the team paid for the project themselves. Matthew says he got the idea in high school, when he watched MIT's 0.38 second robot (Guinness World Records).

Mitsubishi Electric's robot (2024). According to Guinness, the hardest part wasn't the robot but the cube itself: the cube couldn't keep up with the machine and jammed on the very first official attempt. The team had to fine-tune the machine so the cube would stop jamming (Guinness World Records).

4x4 cube robot. Guinness has a separate record for the 4x4 cube. In May 2025, British brothers Matthew and Thomas Pidden did it in 45.30 seconds, beating a record that had stood since 2014. Their robot uses two cameras and four arms; the cameras are covered by a shield until the start, so the machine can't look at the cube ahead of time (Guinness World Records).

How does a Rubik's Cube robot work?

Every Rubik's Cube robot does three jobs, always in this order:

1. Look. Cameras take pictures of the cube's faces, then software reads the colour of each sticker and rebuilds the state of the cube.
2. Plan. A computer works out a sequence of moves that solves that state.
3. Turn. Motors turn the faces of the cube, following the exact sequence it just worked out.

A fast robot needs all three jobs to be fast. According to Purdue University's news page, Purdubik's Cube uses machine vision to read the colours, a solver the team wrote themselves to cut down running time, and industrial motion control hardware from Kollmorgen. Every turn speeds up and slows down along its own carefully tuned path (Purdue University).

Unlike people, a robot doesn't need to memorise algorithms or go layer by layer. It works out a short solution straight away for the exact state in front of it.

The "plan" step: Kociemba's two-phase algorithm

Lots of Rubik's Cube solving programs are based on the ideas of Herbert Kociemba, who came up with the two-phase algorithm in 1992. According to Wikipedia, the aim of the algorithm is to find a fairly short solution very quickly, not necessarily the shortest one. For a randomly scrambled cube, it usually finds a solution of 20 moves or fewer in a fraction of a second (Wikipedia).

The pages about Purdubik's Cube don't say which algorithm the Purdue team used. Below we explain Kociemba's approach, because it's the most common one and the easiest to follow.

If the letters R, U, D and F are new to you, see Rubik's Cube notation for beginners first.

The idea: split the problem in two

Kociemba splits the moves into two groups:

• Free moves: the top face (U) and the bottom face (D) can be turned any way you like.
• Half-turn-only moves: the four side faces (R, L, F, B) can only be turned 180 degrees, that is R2, L2, F2, B2.

Why this limit? Compare the two pictures below. A quarter turn R moves the white stickers of the corners onto the front and back faces:

1. You start with (input)
3. After the formula

But R2 moves the white stickers from the top face straight down to the bottom face. The white and yellow corner stickers still sit on the top or bottom face:

1. You start with (input)
3. After the formula

If you only use U, D and half turns, the corners can never be "twisted" off the top and bottom faces. According to Wikipedia, these moves form a group that is much smaller than the whole cube, so a computer can search for a solution inside it far faster (Wikipedia).

Phase 2: solve with free moves and half turns

If the cube is already in a state that "can be solved with only U, D and half turns", the computer finishes the solve with just those moves. For example, the cube on the left below is solved with four moves, D F2 U' R2, without a single quarter turn of a side face:

1. You start with (input)
3. After the formula

Take a close look: on the left cube, every white and yellow corner sticker is still on the top or bottom face, even though the corners have swapped places.

Phase 1: get the cube into that state

A randomly scrambled cube usually has twisted corners and flipped edges. Phase 1 finds a few moves, using any kind of turn, to bring the cube into a state that phase 2 can solve.

We built the example below to show the idea. The cube on the left has twisted corners: some of its white stickers are on the side faces. The solution R D F2 U' R2 has two parts:

• R is phase 1: after this move, every white and yellow corner sticker is back on the top or bottom face.
• D F2 U' R2 is phase 2, exactly the same as the example above.

1. You start with (input)
3. After the formula

According to Wikipedia, Michael Reid proved in 1995 that phase 1 never needs more than 12 moves and phase 2 never needs more than 18 moves (Wikipedia). Real programs also try lots of different ways of splitting the solve, to find a shorter total.

A computer's solution is usually much shorter than a person's, but it isn't always the shortest possible. The shortest solution for the hardest state is 20 moves, a story told in the post God's Number for the Rubik's Cube.

Why don't people solve like robots?

People can't work through millions of possibilities in their heads in a few seconds. That's why human solvers follow a method that breaks the solve into small steps, like the beginner layer-by-layer method or CFOP. They accept more moves so they don't have to stop and think for long.

You can see the layer-by-layer method, starting from step 1 of the EasyRubic guide:

Robots are the opposite: they plan very fast but depend on cameras and motors. Today, as the Mitsubishi Electric team found out, a robot's limit is often the Rubik's Cube itself, which can't cope with the turning speed.

Summary of the move sequences in this post

Each sequence comes with its picture. Hold the cube with white on top and green in front.

• Quarter turn, twists the corners: R

1. You start with (input)
3. After the formula

• Half turn, doesn't twist the corners: R2

1. You start with (input)
3. After the formula

• Phase 2 example: D F2 U' R2

1. You start with (input)
3. After the formula

• Two-phase example: R D F2 U' R2

1. You start with (input)
3. After the formula

Solve your own cube

You don't need a robot to solve your cube. With the EasyRubic app, you scan your real cube with your camera, just like the robot's "look" step, then see the solution step by step on a 3D cube. Get EasyRubic and try it now with the cube in your hand.

Video

Want to see it in motion? The short video below from the QUỐC TẾ BÁCH KHOA HCM channel on YouTube shows more of what this post is about. The video belongs to that channel and is embedded straight from YouTube.

Sources

• US students build robot that solves puzzle cubes faster than you can blink your eyes – Guinness World Records
• Fastest robot to solve a puzzle cube – Guinness World Records
• Purdue ECE students shatter Guinness World Record – Purdue University
• Japanese company's robot solves a puzzle cube in 0.305 seconds – Guinness World Records
• Brothers smash record with puzzle cube-solving robot – Guinness World Records
• Optimal solutions for the Rubik's Cube – Wikipedia
• WCA records – World Cube Association